L4D2 Sound Mod Creator
The Sound Mod Creator is a program made by "LUKeM a.k.a Neil - 119" over at the l4dmaps community. Its purpose is to simplify the creation of basic L4D2 sound mods. You can download it here[dead link].
How It Works
The tool scans for available Source games and enumerates a list of all available sounds for each game. Then, it allows the user to browse the sounds, filter by name, replace existing sounds with custom MP3s/WAVs/OGGs etc. Moreover, it handles all file type/length/bitrate conversions internally through ffmpeg. Lastly, the program can package VPKs for sharing sound mods with friends.