Edcast - Download Link
Standalone or DSP for Winamp. Encode HE-AAC, AAC, MP3 and Ogg Vorbis streams for Icecast and Shoutcast servers. Free! (Recommended)
Shoutcast DSP Plug-in for Winamp - Download Link
Encoder for HE-AAC/aacPlus v2, MP3, MP3Pro. Stream to Icecast and Shoutcast servers. Free!
SAM Cast Pro - Download Link
Encode HE-AAC and MP3 for Icecast and Shoutcast servers. Encode WMA for Windows Media servers. This software also includes built in 'Sound Processing'. Free 14-day trial, buy for $199.
SAM Broadcaster - Download Link
Radio automation software with built in encoders for HE-AAC, MP3 and WMA. Free 14-day trial, buy for $299.
Microsoft Expression Encoder 4 - Download Link
Encoder for Windows Media Audio or Windows Media Video streams and servers.
Nicecast (Mac OS X) - Download Link
Mac OS X encoder for MP3 streaming. Streams to Icecast and Shoutcast servers. Free 14-day trial, buy for $59.
Flash Media Live Encoder - Download Link
Encoder for H.264 and VP6 video streams for Flash Media Server and Wowza Media Server. Free!
QuickTime Broadcaster (Mac OS X) - Download Link
Encoder for H.264 video streams for Darwin Streaming Servers.
Wirecast Live Encoder (Win & Mac) - Download Link
Encode H.264 and VP6 video streams for Flash Server, Wowza Server or Windows Media Server.
Orban Opticodec-PC - Download Link
Encoder for HE-AAC/aacPlus v2 streams. Stream to Icecast, Shoutcast, Adobe Flash, Wowza Media & Darwin Quicktim servers.
The below free software applications will monitor the presence of audio on the recording line of PC sound card.