For a long time, I used Quicksilver until it went un-supported for some time (or let’s say less supported for a while). Nowadays, I use Alfred. Alfred is Spotlight on steroid and makes multiple actions and workflows accessible via keystrokes. Version 2.0 is now out and Cult of Mac has a nice article: Great Workflows To Help You Get More Done With Alfred 2.0 [Feature] | Cult of Mac.