Merlin lists the apps he discussed at OSXCon. A few cool ones I hadn't heard of before:

• Notational Velocity, a notes program with emphasis on ultra-simplicity, all-keyboard access and incremental search. That's one weirdly written web page; the download link is at the very bottom, outside of the border. Free.
• VoodooPad, another notes program with emphasis on versatility and multimedia. Self-described as Wiki for the Mac desktop; I'd need network/Internet sharing of notes to take that claim—and this would especially rock if it had such a feature. Looks cool as it is. $20.
• Growl, a notification platform, of sorts. Instead of having each app tell you about stuff in its own way (Mail goes ding, AIM pops up a little box), Growl watches for events and tells you about them in any of several ways you decide. Features an API with bindings in many languages, so your scripts and custom apps can notify you as well. Free.
• GeekTool is a sort of system monitor that can spew logs, show graphs and run commands in foreground and background windows or onto the desktop. Would be especially useful for servers or development environments.
• fiwt, incremental search for Safari. After Mozilla/Firefox introduced find-as-you-type, I haven't been able to live without it. Free.
• I-Search Plugin, adds incremental search to most Mac OS X text boxes. Sweet. Free.
• PathFinder also gets a mention because people asked Merlin about it (it wasn't part of the talk). I haven't given this Finder power boost a try yet, but I've been meaning to. $34.

O'Reilly's Mac OS X Innovators stuff includes articles about winners of their contest from this and previous years, and other articles.