When it comes to sex it is hard to say what is or isnt "normal". What is normal is what both partners feel comfortable doing in the privacy of their homes.
Some men find anal stimulation very arousing. This doesnt mean that they are gay or even bisexual. The anus has nerve endings which some men enjoy being stimulated. Some men want anal penetration so that their prostate gland is massaged which produces intense stimulation and can even lead to ejaculation.
Taking appropriate steps to make sure the anal area is clean and making sure that the partners wash thoroughly with soap and water after any anal activity and before any other sexual contact is important.
Yes, it is normal. Don't get freaked out. And it does NOT mean you are gay. Like MrNice said, there are many nerves in that area that are very sensitive and can bring great pleasure. Most men are too homophobic to experiment with this area and our culture tends to frown upon it. No matter what, you are normal. Not to worry.
I think it's very normal, though not as common as it would be if men would let go of their rediculous fears of it being a homosexual thing. I've always liked it, but was married for almost 10 years before I felt comfortable sharing my interest with my wife. I was so relieved when she was open to it and didn't think it was wierd. Now it's a fairly common part of our foreplay and I love it because it feels awesome. Sometimes I even like just a little bit of penetration with a small vibrator to stimulate my prostate, but most of the time just touching around my anus is what feels best. Just make sure you're partner is freshly showered and clean down there.