Up to crazydreams.org

Collections Development Resources

Your best bet for finding out not only what is popular but what will be popular when it becomes locally available is to make friends with several anime fans with differing tastes who know what's getting a lot of attention in the world of fan subtitling (fansubs) and elsewhere online. Beyond that, the following are some useful resources:

Anime News Network (ANN)
Good for general information, but the viewer ratings should be taken with a grain of salt. Good for finding related series. Good for tracking individual creators, voice actors, and companies.
Unfortunately, reviews sometimes reflect personal biases of the reviewers.
Weekly sales rankings
What's popular. (Not collected as a separate section, but subsequent weeks are listed as "follow up" articles and linked to.)
"Buried Treasure" column
A good source for quality anime that doesn't appear on the weekly sales rankings.
Anime on DVD
Now part of Mania.com, AnimeOnDVD.com has checklists of all releases and other useful resources.
Anime Database (AniDB)
Good for tracking relationships between series.