Onepagex.com is an online tool that convert crypto currencies quickly, Onepagex.com has over 140 cryptocurrencies list.
More importantly, STEEM has been integrated as a base asset.

Onepagex.com Step on how to use it.

Pick the cryptocurrencies you want to trade.

Enter your withdrawal address (In this case we are converting STEEM to LTC so we type in an LTC address).

And lastly Following the instructions, deposit the amount of STEEM you want to convert and observe the status indicator at the bottom of the card for transaction progress.

Onepagex.com video

This video showcase the steps and feature of Onepagex.com