Sometimes, you'll encounter URLs in text that aren't active links. That is, you can see the URLs, but clicking on them won't open the requested page in your default browser. Instead, you're forced to copy and paste the URLs, or Control-click (right-click) and choose Open URL from the contextual menu. Hints reader McYukon discovered a Lion shortcut for opening URLs that you come across in Terminal. It could come in handy if, for example, you use Terminal to look at Read Me files or other text documents.
The trick? Hold down the Command key as you double-click on the URL. That's it! And it works even if the URL you encounter lacks the http:// portion; Command-double-clicking on www.macworld.com works just fine.
It's worth experimenting in other apps, too. BBEdit, for example, offers the same functionality, though the behavior doesn't appear to be supported system-wide.