There are many variations of the
Rabbit, but the thing they all have in common is a dildo piece that goes inside the vagina and a stem coming off it that stays outside for clitorial stimulation. Some of them also have rotating part on the dildo piece as well. Lots of people really like them - we haven't tried them personally, so I couldn't say if they are worth it or not.
From what I've heard, you can't go wrong with the Magic Wand I linked above, but you may be looking for something a little more portable (the Magic Wand plugs into the wall) and quieter (possibly cheaper too..the Magic Wand will set you back about $50 or so).
Check out
The Vibe Guide and
How to Choose a Vibrator on women.com for a good introduction to what's available and how to make your decision.