Your Google+ profile ID is a horrifying string of meaningless numbers. For example, mine is 111203177111013925515. Gah! Here's how to pretty it up.
That Google+ profile address looks like crap on the Web, and even worse in an email signature. But if you want to share your profile, and make it easy to remember, head to Gplus.to. It's an easy vanity URL-shortener that will let you create a handy nickname that redirects to your Google+ account. So instead of user 111203177111013925515, I can just be Gplus.to/mth.
Act fast. The short handles will run out quickly.
Update As ehed points out in the comments, if you already had a Google profile set up before the Google+ launch, that address (such as http: //profiles.google.com/yourusername) now points to your Google+ profile.