Alone, Together - Absolutely incredible Kim Possible fanfic. Probably the best fic I've ever read, period. I don't care for the show, but I do love the Kim x Shego fandom.
Subtext Is So Not The Pretext - Another great Kim Possible fanfic. Lots of naughty scenes in this one, but a great plot to go with it.
Recommended Yuri Manga:
Kase-san - An adorable story centering around Yamada, a kind of awkward girl with an interest in gardening, and Kase, a popular track team member.
Strawberry Shake Sweet - Very, very enjoyable manga with both romantic elements and a lot of great comedy. In this story, Julia, a veteran idol, mentors Ran, a new up-and-comer.
Murcielago - A more mature, but still highly comedic manga featuring a skilled killer, Kuroko, who works for the police and has an insatiable love for other women.
- A story of two high school girls, Nan and Sei, and their motorcycles.
Girly - Can't remember for the life of me how I came across this, but it's got some great girl/girl romance elements and it's just downright funny as hell.
OverlordJC's DeviantArt Page - JC did the cover art for "A Midsummer Night's Beauty" and has also done a lot of other great Ranma and Shampoo art. Go pay him a visit.
MegaPhilX's Shampoo Gallery - MegaPhilX did the cover art for "Pawprints in the Snow" and has done a ton of other Shampoo art over the years. Go check out the rest of his work.
monmusu.prettyanonymo.us - For your Everyday Monster Girls manga scanlation needs. Very good and amusing manga about...monster girls, of course!
Manga Stream - For your Hajime no Ippo and One Piece manga scanlation needs, among others. If you want to see what's been happening in those stories beyond what you've seen in the anime, you should definitely check them out.
MyAnimeList - Awesome site for rating anime you've watched and communicating with other fans.