The Interactive Fiction Archive is of course the ur-resource for all things IF.
- The Interactive Fiction Wiki
- The Interactive Fiction Community Forum — just what it says on the tin.
- The Interactive Fiction Database is the closest thing we have to a social networking service.
- iFiction: hundreds of titles playable online.
- Classic Adventures Solution Archive
Website of the ifMUD, the community’s oldest hangout besides the now defunct newsgroups.
Books and Publications
- SPAG Magazine
- Brass Lantern
- Planet IF (arguably not a publication, but fits here).
- Teaching and Learning With Interactive Fiction
Too many authoring systems to list, but Roger Firth’s Cloak of Darkness provides a good overview.
Last but not least, here’s another resource list by Emily Short.