WinRAR:

Use this to uncompress files that are in rar, or zip format.

Sonic Adventure DX:

Switch Sound File Converter:

Use this to convert MP3 and other sound files to wma and wav for music and sound effect hacks in SADX.

SADX Sound Effects Hacking Pack:

Use these programs to uncompress and compress the DAT files that SADX uses for it's sound effects.

PVMedit:

Use this to open SADX's PVM files and edit them.

Sonic Heroes:

Sonic Heroes Charrepper:

Use this to replace characters' animations and models in Sonic Heroes without the game crashing

TXD Workshop:

Like the PVMedit for Sonic Heroes. Use this to open and edit Sonic Heroes' TXD files.