I like to use gist for sharing code snippets. I like to use QuickSilver for automating common tasks. To combine the two is fairly simple:
  1. Install the gist gem
  2. gem install gist

  3. Enable the Terminal Module in QuickSilver Plug-ins
  4. Create a new HotKey Trigger
  5. Hit "." then type the following command into the Select Item field. You only need the bash part if you installed the gist gem using rvm/ruby instead of the system ruby
    bash -l -c "pbpaste | gist | pbcopy"
  6. Tab over to Action field, and select "Run Command in Shell"
  7. Save the trigger, then set whatever hotkey you want - I use Cmd-Shift-G - you might need to restart quicksilver for this to take effect
Now you can select some text, copy to clipboard, then hit Cmd-Shift-G to create a gist from the clipboard contents, ending up with a url to that gist now in the clipboard.