Of the three search tools, Podcast.net and Yahoo Podcast gave me the best results, and pretty much the same results. I've added three new podcast feeds to my blogslines: "A Few Appropriate Remarks," a 24-episode series from EverythingLincoln.com, "The Abraham Lincoln Logs," from the website of the same name, and "100 Word Short Stories," a series of podcasts which include "The Wacky Adventures of Abraham Lincoln." That one didn't sound promising to me either, but I subscribed to it anyway.
"A few Appropriate Remarks" from EverythingLincoln.com, is a series of elaborately produced podcasts with visual effects and background music to the narration of historical facts about Lincoln. They actually did a very nice job on these.
"The Abraham Lincoln Logs" are political satire. Lincoln comments on AT&T iphones, talks to Dick Cheney, samples the latest videogames, and says something to offend everybody. Usually Lincoln impersonations leave me cold, but these grew on me.
"The Wacky Adventures" are 100-word short stories created by Laurence Simon. They have very catchy punchlines and are accompanied by the text so that you can read while you listen. Caleb Bullen's narration is better than Simon's. By the way, you can submit your own entries to the "100-word" site on any topic.
One thing I've learned about podcasts -- the delivery is everything. Like audiobooks, the voice is all you have to go on, so the narrator can either make or break a podcast. There are many fine ones out there, including a short series on the Civil War from the Pritzker Military Library through lib.worm, which I also saved to my blogslines.
The future of podcasting in a library setting has already taken the form of NetLibrary audiobooks. NetLibrary has had some trouble with their links, but ideally, when conveniently accessed through a website, or updated through RSS feed, these podcasts can actually replace the physical audiobook collection. It's one more step toward the library without walls.