[Stratrat]

I like the Roland Micro Cube better than the various Pods, headphone amps, etc. because you can use headphones and play totally silent when you need to, but you also have a fun little amp for the times when you can actually unplug the headphones and make some noise. It can get surprisingly loud for such a small amp.

Another neat alternative is the Boss Micro BR. It can be used as a headphone amp and has onboard effects, amp/cab simulations, etc., but it's also a very capable little 4-track recorder. It has programmable drum sounds, a phrase trainer which allows you to slow music down to learn licks, etc.