Lots of cheap desktop mics are available on ebay [7].
Here's a typical condenser microphone [8].
Great collection of microphones and accessories [9].
Great microphone "shoot out" [10] at Transom.
Links:
[1] http://rabble.ca/podcasts/shows/podcast-diy
[2] http://rabble.ca/taxonomy/term/1921
[3] http://rabble.ca/audio/by/artist/wayne_macphail
[4] http://rabble.ca/audio/by/title/diy-2005-10-22
[5] http://rabble.ca/audio/by/album/podcast_diy
[6] http://rabble.ca/audio/by/genre/podcast
[7] http://search.ebay.ca/desktop-microphone_W0QQfcdZ2QQfclZ3QQfnuZ1
[8] http://namm.harmony-central.com/WNAMM03/Content/Behringer/PR/B-2-Pro.html
[9] http://www.soundprofessionals.com/cgi-bin/gold/category.cgi?category=0
[10] http://www.transom.org/tools/recording_interviewing/200508.mic_shootout.html#
[11] http://rabble.ca/user
[12] http://rabble.ca/user/register