Yeah, I'm switching again.
I'd used Notational Velocity before, and really liked it, but switched to DevonThink PE to manage stuff that I don't necessarily want Google to find (password, bank account info, and random notes - code snippets and the like - that don't make sense being blogged)
I just tried the full DevonTHINK Professional edition, and while it's really nice, and has handy Dashboard widgets for easy access, it just struck me as a "heavy" application. Its interface is essentially a taxonomy, or a hierarchy of folders. That's cool, but you need to keep thinking about where to meaningfully store stuff.
I was tossing around the idea of using a personal wiki (TiddlyWiki, WikitiWidget, a local copy of MediaWiki, or VoodooPad), and then remembered Notational Velocity (well, remembered isn't the word... I saw the icon sitting next to VoodoPad in my ~/Applications directory :-) )
NV is really sweet. It's basically just a tagging interface - you type in a tag (or a "description", in NV-speak), and it searches all of your notes, providing a list of relevant items. If you hit TAB to get into the text entry/display field, you can create a new entry for that tag/description, or edit an existing one. It's one part wiki, one part fulltext index, one part tagging. No hierarchy. No taxonomy. Just fast, simple entry and retrieval of information, without any bells or whistles getting in the way.
I've bound it to respond to "control+space" so it pops up with a single keystroke for easy access.
Update: Well, it gets even easier. NV has a couple of system-wide Services available. Hit "command+shift+v" and your text selection gets turned into a new NV entry, with the first line being used for the "description" (tag), and the entire selection used in the body. Sweet.