HOWTO: Broadcasting to an Icecast Server using the Oddcast DSP plugin for Winamp
Icecast2 supports Ogg Vorbis and MP3 streaming and has many other features as well. Before continuing with this HOWTO, you need to have both Winamp and the latest "Oddcast DSP plugin for Winamp". Please take a moment to download and install those programs at this time if you have not already done so.
Step 1 - Accessing the Oddcast Plugin Preferences:
In order to broadcast audio to an icecast server, you will need the hostname, port, password, and mount information for the icecast server. Once you have that information, you need to open Winamp and press control-P. This will open the Winamp preferences dialog window. In this dialog, under "Plugins" you will find "DSP/Effect". Click there to access the plugins preferences section.

Now select the "oddcast DSP v3" plugin in the list of available plugins.
Step 2 - Configuring the Oddcast DSP Plugin:
You will need to add an encoder with the "Add Encoder" button to set up a stream to the server.

After you add an encoder it should show up below the "Add Encoder" button. You can then right-click on the encoder and choose "Configure".

The "Configuration" window will open and start you out on the "Basic Settings" tab. If you did not configure the Icecast2 server yourself, you may need to ask an administrator of the server for some of this information. Set the settings on this page to match the settings of the server you are broadcasting to.

Next on the "YP Settings" tab you can configure your Yellow Pages listing settings. Leave the "Public Server" checkbox unchecked to not list this broadcast in the Yellow Pages directory.

Next on the "Advanced Settings" tab you can check off the "Save Archive of Stream" checkbox to save a copy of the broadcast to the hard drive in MP3 format. Alternatively, you could also check off the "Save as WAV" checkbox to instead save the broadcast to the hard drive in WAV format. If you wish you may also like to save a logfile, specifying a higher loglevel the more you want it to log.

After setting all the settings press OK and you will return to the Oddcast window. Make sure your soundcard is selected, and the levels are okay, otherwise make any needed adjustments in Windows Volume Control. Press the "Edit" button at the top to edit your Metadata (the information containing your name or the name of your broadcast which you will send to the Icecast2 server. Highlight the encoder at the bottom of the Oddcast window and press the "Connect" button.
If you have troubles getting the MP3Lame option to show up in the dropdown list of "Encoder Types" make sure you've placed your lame_enc.dll in C:\Program Files\Winamp.
That should be it!