Supposedly Texas Instruments TI-99/4A BIOS ROMs and Texas Instruments cartridges can be granted permission to distribute for personal use, though not permission for commercial use and definitely not extending to the third-parties that also made software for the TI-99/4A.
I finally found the permission granted to one such person I've remembered for years (attn: mizapf, Justin) though I also remember seeing an older permission:http://tech.groups.yahoo.com/group/ti99-4a/message/4682?var=1
Other TI-99/4A emulator authors supposedly with permission:
Also, they have granted permission to distribute TI99/8 ROMs
Also, 99er.net has permission to distribute scans of TI-99/4A manuals: http://www.99er.net/files/TIpermission.pdf
However, in the past they've sent C&D's regarding calculator ROMs.http://www.geocities.ws/joelt49/calc/calc.txt
Still, if you're opening a ROM site to distribute Texas Instruments TI-99/4A ROMs, you have to contact them and ask for permission - you can't take someone else's permission (Classic99's, PC99's) as your own.
For other ROMs in general, you may also like:http://blog.makezine.com/2008/12/27/retro-gaming-emulators-that-include/
There is no massive list of PD/free ROMs/BIOSes/firmware and software/cartridge images/etc. but it would be nice if there were...