I found this article really helpful with getting an understanding of Regular Expressions which are really useful for defining goals and funnels in Google Analytics.
Analytics Talk Blog Archive My Regular Expression Tool Box
Say for example you have a goal url like so:
/example/widgets/blue/checkout
/example/widgets/red/checkout
You can cover both of these url's as 1 single goal url in Google Analytics using the OR operator
/example/widgets/blue|red/checkout
Also useful when using your TOP Content Report and trying to filter out Page Titles or URL's.
You can also use regular expressions to exclude IP ranges from your reports, useful if you want to exclude internal traffic on your website etc..
