I've expanded the types of files that may be attached to forum posts, as well as the sizes allowed.
Audio Formats:
ac3 - 8MB - Dolby Digital AC3
mp2 - 8MB - MPEG Layer II
mp3 - 8MB - MPEG Layer III
mpa - 8MB - MPEG audio (Layer II or III)
wav - 8MB - PCM uncompressed waveform
Video Formats:
avi - 8MB - AVI wrapper video file
flv - 8MB - Flash video wrapper (usually On2)
m2v - 8MB - MPEG video elementary stream
mp4 - 8MB - MPEG-4 (usually H.264, sometimes Divx/Xvid)
mpg - 8MB - MPEG video program stream
wmv - 8MB - Windows Media video
Image Formats*:
gif - 100kb - GIF compressed graphic
jpeg -100kb - JPEG compressed photo
jpg - 100kb - JPEG compressed photo
png -100kb - portable network graphics
psd - 8MB - Photoshop document
* Images will be resized on upload, so you may need to stick high-res images inside of archive files!
Archive Formats:
rar - 8MB - RAR compressed archive
zip - 8MB - ZIP compressed archive
sit - 8MB - compressed archive, mostly used on Mac
dmg - 8MB - Mac OS X installer
Document Formats:
doc - 5MB - Word doc
pdf - 8MB - portable document format
txt - 1MB - plain text
vcf - 100kb - VirtualDub settings file
xls - 8MB - Excel spreadsheet
This should cover most anything that is needed for upload on the forum.
WARNING: Note that all uploaded archive formats will be scrutinized by admins, and malicious/worthless files will be deleted.
Don't waste your time or ours with crap/spam uploads. Junk will be removed almost immediately.