GRC:Gridcoin possibly has the best story of all cryptocurrencies (equal to the Bitcoin mysteries, as far as I'm concerned), but for some reason no-one is broadcasting it.
Gridcoin will pay you to help solve Earth's problems & advance the sciences.
You can contribute & earn on virtually any device you can think of.
Anyone can help & earn, even if their only computer is a phone.

Gridcoin created a unique consensus method deemed DPoR (Distributed-Proof-of-Research) which was modeled from PoW, then coupled with their guaranteed minimum 1.5% APR PoS Minting system. This developed a stable incentivized economy atop the world's largest computing grid, BOINC (Berkeley-Open-Infrastructure-for-Network-Computing, est. 2002). Gridcoin was also the first cryptocurrency to utilize BOINC.

BOINC was originally created to manage the first dApp in history, SETI@home (Search for Extra-Terrestrial Intelligence). By donating computing power, people globally helped search the sky for alien radio signals & other signs of life while BOINC secured the network by keeping score of & proving who helped the most. Fifteen years later, BOINC is Earth's largest network at 17 PetaFLOPS with over 30 contributing science projects. 25 projects are currently voted by Gridcoin users to be on their white-list.
BOINC projects did this by creating specialized programs to utilize nearly any computer device in the world. Five projects have devised specialized programs so even a Raspberry Pi can profitably contribute to BOINC & profitably mine Gridcoin.
By allowing users to decide what percentage of which computing resources on which devices are used, for how long & under which various circumstances, computing Work Units for any BOINC & Gridcoin white-listed project is able to mine Gridcoin with as little hardware stress & electrical consumption/cost as possible.

Any CPU or GPU can be used, as can some specialized sensors. Included are unmodified or slightly modified Geiger counters & specialized radiation sensors, seismic or other QCN motion sensors built into laptops & mobile devices (for shock/drop protection, but now earthquake detection), & meteorological sensors.
Some project programs are made to run on Windows, Mac OS X, Linux, Android, VirtualBox, & FreeBSD. Other programs are designed to optimally run on specific hardware such as Intel CPUs, NVIDIA GPUs, AMD GPUs, & even the Raspberry Pi.
The integration of various sensors, coupled alongside its customized mining, permits Gridcoin to enjoy permanent & perfect ASIC resistance thereby remaining able to allow ASIC devices to secure nodes, process transactions, & broadcast Beacon smart-transactions. The Gridcoin community allows the use of Scrypt ASIC mining.
Only Gridcoin may be profitably & safely mined on a new or old phone, tablet, game-console, TV-box, SmarTV, Raspberry Pi, some cars, new refrigerators, or a TI-83+ calculator.
No other coin can offer the same level of direct control over your device resources.
Forget about having to worry whether or not you'll hurt your laptop, desktop, or server by running BOINC to earn rewarding payouts.

The Gridcoin wallet has an inbuilt Neural Net displaying the aggregated data of white-listed projects, valid vs. active CPIDs (Gridcoin account identifiers to the BOINC network), which CPIDs have signaled an active Beacon in the last 6 months, each CPID's first generated address, CPID Total RAC (Recent-Average-Credit), CPID average RAC, CPID Magnitudes, Gridcoin Whitelist project names, project Total RACs, project average RACs, Network traffic, charts regarding your contributions to all projects, etc.
CPID are necessitated of Gridcoin by BOINC as a forgery-prevention method regarding each CPID's completed Work Units for each project, therefore the Gridcoin network cannot currently achieve stealth regarding any wallet's contents or transaction history. However, you're pursuing & aiding a noble cause (or twenty-five) & getting paid for it, you should be proud!

Putting aside the vast number of global BOINC contributors who foolishly don't utilize Gridcoin, my analysis of Gridcoin client's Neural Net showed there were currently a mere 2,935 active CPIDs with signalling Beacons, many seemingly abandoned or without RAC earned. There are only 1,575 fully functioning CPIDs, plus two large pools (grcpool.com is the largest) & ten small to mid-sized pools/institutions.
Admittedly, the previously stated number of earners is skewed by grcpool.com & other pools who collect BOINC credit on a single CPID. These pools are occupied by the thousands of prospective investors with too little money to stake effectively, no computer to constantly stake from, minimal computing power to contribute to DPoR, or too little time/knowledge/motivation to get set up properly or research how.

How does it work in practice?
There's apparently a lot of confusion out there.
There're certainly a lot of poor guides. I'll make it simple.

1. Download the latest Gridcoin core client from GitHub.
2. Download the latest "BOINC Manager + Virtual Box" .zip from Berkeley.
3. Sync the wallet.
4. Deposit Gridcoins to your wallet. Recommended >5,000-GRC to stake reliably.
5. While your wallet syncs, access the wallet Neural Net to check the Gridcoin Whitelist for which projects have the lowest average RACs.
6. a. Unlock the wallet fully, not just for staking.
   b. Reserve 10.1-GRC for spending, ensuring Beacons are sent automatically for 5 years.
7. a. Get your Beacon sent & signalling. If it didn't do so automatically (the client overview page under Client Messages will error), open the debug console & type 'execute advertisebeacon'.
   b. Pour a drink if that was your first smart-transaction. Say "Hooray."
8. Close the wallet.
9. a. Edit the wallet's .conf file.
   b. Populate it with your email address.
10. Restart the wallet.
11. Unlock the wallet for staking only.
12. Open BOINC & decide upon projects to assist. Perhaps you're not an idealist....maybe you don't care who you help in this crazy messed up world so long as you get your fat got-danged paycheck. Well, to maximize your DPoR mining rewards you must ensure you contribute to BOINC projects with the lowest average RAC. This gives you the opportunity to surpass the average RAC of a given project's average contributor. Doing so magnifies the Credits received for any Work Units your devices complete. Your average RAC from each project is calculated against theirs & other factors are compiled to determine your CPID's network Magnitude. Magnitude is the final figure used to determine your DPoR rewards against block difficulty.
13. a. Joining a project takes you to an account creation page. Choose a username.
    b. The next page is a search for teams. Search "Gridcoin" & click the result.
    c. Beneath the team description, click the link 'Join the team'. Your Beacon has now connected that project, team, & account to your CPID.
14. a. For security & optimization purposes, open your account page on each joined project.
    b. Under 'Preferences', select the link next to 'Preferences for this project'.
    c. In the center of the next page, select the link 'Edit Preferences'.
    d. Deselect the checkbox next to 'Is it OK for [project name] and your team (if any) to email you?'
    e. Select/deselect whichever hardware & software components apply to your devices to receive optimal Work Units.
15. a. Return to your account page.
    b. Under 'Preferences', select the link next to 'When and how BOINC uses your computer' which says 'When and how BOINC uses your computer'.
    c. Optimize the project's utilization of your computing resources to reduce electrical cost & hardware stress.
16. In BOINC client, click Project Commands & select Update (do this for each project).
17. Earning BOINC credits for GRC on your Android, Windows, Linux, or iOS device is as easy as downloading the BOINC app from the Google Play Store or Apple's App Store, no need to install GRC wallet on every device as well.

Hope you've enjoyed the simplest walkthrough yet, friends.
Friend Lawful on the projects you join!