I went to youtube, and it's pretty heavy on his IWA work. Now, I'm a ROH fan, so some of it was new to me.
The Eddie/Rey/Punk triple threat is a classic. And the OVW clips are cool too (I don't have enough money for both ROH and OVW). But... if you're looking for what got Punk all the buzz, here are my recommendations, depending on taste.
If you like the Hardcore stuff, check out Death Before Dishonor (vs. Raven), The Conclusion (vs. Raven), Death Before Dishonor 2 Night 2 (with Ace Steel vs. Dan Maff and BJ Whitmer) or Manhattan Mayhem (vs. Jimmy Rave).
If you want great technical wrestling check out his amazing series against Samoa Joe. The shows for those are World Title Classic, Joe vs. Punk 2 (catchy, huh?), and All Star Extravaganza 2. He's been in a lot of good ones, but those 3 matches are considered by some to be the new millenium's Flair/Steamboat.
And if you want to see some great promos, check out Wrestlerave, Joe vs. Punk 2, Death Before Dishonor 3, Sign of Dishonor.
Yeah, this was sort of shilling Ring of Honor, but that's really where Punk made his name.