Launchers

I first encountered launchers on someone's list of "essential Mac software". I had no idea what they would do, but I downloaded Quicksilver to give it a try. I've been hooked ever since. Here are, as far as I have found, the best Mac and Windows launchers out there:
MAC

• Quicksilver is what I use. You can change it's look, add commands (actions), and set tons of different preferences.
• Butler seems to have very similar features, and thus it's own following. I haven't tried it, so I don't have much to say about it, but with fully customizable menus, it looks like it may be better than Quicksilver.
  
• LaunchBar costs money. That means I haven't tried it and probably never will.

PC

• Colibri looks a lot like Quicksilver, but without nearly as many plug-ins available.
  
• Launchy also seems pretty basic, but it's open source, so there's a better chance someone will develop some more complex features. So far contributors have just created skins, though.
  
• AppRocket costs money, and doesn't seem to do more than Colibri or Launchy.
• PC-Com is just plain Windows-looking, but it does have a few extra features, like notes and reminders. Worth looking into if form follows function for you.
  
• SlickRun is also very Windows-looking, but it lets you create aliases for commands.