Your backside will toughen up eventually (fairly quickly too) if you keep riding. One secret is to not ride for any long duration all at once. Many shorter rides are better than one long ride in the caboose department. Get up out of the saddle once in awhile too.

If you're sore at the start of the ride, then you need to ease up a bit and let your tissues heal. If you're getting seriously sore during the ride, then shorten your time in the saddle. You should also get off the bike every 15 - 20 mins and walk around. Good time to rehydrate and eat 1/4 of your powerbar.

A better saddle may also help. Selle Italia and Specialized make some decent products that is liked by a lot of folks. What saddle you should buy is a personal fit issue. I love my Selle San Marcos but don't like the Flite saddles. Most LBS's have an "exchange" program where you buy a saddle and ride in it once/twice. If it fits, fine. If not then you can bring it back and "exchange" it for a different one to see if that works.

Hang in there, it gets better.