In the US the most popular are called "hen and chicks" in the UK they use the proper latin name sempervivum or house leeks. These are a good 'gateway' plant into succulents. They are low growing and cool almost geometric and you can just pull off their little 'chicks' (babies) and put in a pot of grit and low quality soil with good drainage and they root. They are very hard to kill. SO many varieties though and great colours cool blue/green, bright chartreuse. Check them out!