When i joined up with AnySoldier this past winter, it took me FOREVER to figure out how to select my "prey". Eventually, i settled on Afghan as my focus, if for no other reason, the winters are wicked cold, and it seemed like there were fewer requests per soldier. I also tend toward larger groups because it seems like they appear overwhelming and may frighten off some potential supporters with limited resources, such as myself. But, we are Americans and one thing that sets us aside is that so many individuals will stand up and rise to the occasion, that we ultimately accomplish our goals. And we may never meet. But if we do, we feel like we've known each other all our lives. 
Some groups i have been supporting include:
Bruce Anthony (departing 04/2009) 166 soldiers 32 requests at the time he was medivac'd (i'm waiting to hear from his alternate on how to reach him and also how to find out how 1SG Anthony is doing; sending pkgs in the interim anyway)
Joseph Temple (departing 06/2009) 75 soldiers, 21 requests
Paul DerMiner (departing 01/2009) 205 soldiers, 25 requests
Ted Howard (departing 06/2009) 130 soldiers, 31 requests; these guys are really isolated
Joseph Richard (departing 05/2009) 105 soldiers, 21 requests
Barry Moose (departing 07/2009) 125 soldiers, 28 requests
Annette with Bogie Basset, Allie Basset, and Zoe Basset