[mcormier]

Namely is a less complicated alternative to Quicksilver on OS X. It only works for applications. http://amarsagoo.info/namely/

Enso is interesting alternative to launchy on Windows. It's no longer in active development. http://humanized.com/enso/launcher/

[sp332]

I really like Enso for Windows. Half of their dev team went to Mozilla to build Ubiquity, which is a similar idea for web services instead of apps: https://ubiquity.mozilla.com/