Monster Database
Use this to search for monsters and look at their stats.
You can also roll encounters for monsters. This uses their listed amounts (e.g. 2- 12), rolls their hit points, and will list them in a somewhat idiosyncratic shorthand form in the textarea below. Monsters are labeled with their first letter and a number to identify them, so if you roll up 3 goblins you will get G1, G2, G3, and so on.
Note: There is a bug currently where you will get more monsters than you rolled for if they share a substring (e.g. you roll "goblin" and get "hobgoblins" as well). I have no plans to fix this right now as I use it more as a feature (less typing at the table). I suggest you just ignore the extra generations.