I use a combination of files (.sql files, .cs files, etc), OneNote, and Google. Not very elegant, I know, but it works.
I tried this one out once upon a time: http://www.snipitpro.com/. I didn't buy - it was $40 at the time I downloaded it and then they raised it to $50 IIRC. I see now that it is back to $40 which, to me, is too much. I'd pay $20 max for such a system. I've survived 12+ years without paying money for a standalone code snippet manager so to get me to pay money, your system has to be great (which, IIRC, this one was) but it also has to be so cheap that I think to myself, "You know what? It's actually worth the $14.95 to replace my text files and OneNote combo."