Snipplr — Online Sharing of Code Fragments
Each code fragment can be tagged which makes it possible to later do a simple tag based search.
The neat thing is that you can submit and retrieve code fragments from within TextMate. Watch their screencast for an example of this.
My only objection is that Get Snippet uses ⌃⌥⌘P as key equivalent, which is overloaded to do Preview for various markup languages and Show Web Preview (mostly for HTML) — but that is easy to change.