Here's a tip borrowed from the Vim help file. Say that you have a list of names like:
and you want to change that to:
You can use the following substitute pattern to easily do so:
:%s/\([^,]*\), \(.*\)/\2 \1/
Basically, you're capturing zero or more NOT commas followed by a comma and space and then capturing zero or more of anything. The comma and space are outside the parens, so they're not stored. The parens store the captured groups in the special variables \1, \2, \3, \N from left to right, so the replacement pattern is substituting in the groups in the reverse order they were captured.