I have been using one of theese for more than 3 years. It is big enough for up to four cups and is easy to clean.

I bought this Kenwood Frothie CL428 into work one day so I could enjoy a gorgeous hot chocolate. My boss loved it so much, he bought it off me! Naturally, I bought another, but it was the CL628 model. It was so much easier to clean!
So, although I loved the original model, and would recommend it, I'd recommend the CL628 first!
I have been looking for the CL628 for about a year as mine ceased heating (I think I wore it out!). The fact that everywhere I try is out of stock, shows how popular it really is.