ALL2LAME is a free Windows front-end for the LAME MP3 encoder. It's very easy to use:
ALL2LAME is pretty useless without the LAME MP3 encoder. You can get LAME here.
Tag (by Case) can be used to add ID3 tags to the files.
Download ALL2LAME v1.9.1 (it's only 40 kb and freeware)

If you get an error when you try to run the frontend, you need one of the following files (the error message indicates which one):
What's new in v1.9.1:
What's new in v1.9:
ALL2LAME is based on the source code of vbLamer by Chetan Sarva (website is gone).