Amazon has a list of public AMIs:
But this list is sorted by date, not popularity, so it's practically useless for finding good AMIs, unless you know in advance what you're looking for. IIUC, There's no way to tell between a super-awesome AMI with thousands of users and a lame AMI that no-one uses.
Is there a popularity-sorted list of AMIs anywhere on the web?
Amazon keeps their usage statistics completely confidential, so there's no such list unfortunately.
Although from my own experience using EC2 it's always good to trust the following kind of images
This kind of AMIs will guarantee super awesomeness and also super documentation and support