My old roommate used Adam4Adam a lot. Seems like a good site and a pretty good age spread.
Squirt.org seems to be more for cruising than hooking up. I guess I see them as a slight difference (cruising being more public sex, versus having a guy come to your house). Not only that, it seems like most of the guys on squirt.org are in their 50s/60s. If that's the age range you're going for, there ya go.
Gay.com just isn't what it used to be. I was on yesterday but only log on about once every two or three months. Also older guys, but probably more around the 40s/50s range.
There are several applications for the iPhone/Droid that I think has taken away a lot of traffic from gay.com and other sites. Depending on your preference of guys, you could use Grindr, Scruff, or Growlr. Grindr is specifically guys in your area. It shows the 100 guys closest to you. The other two apps show guys near you, and also a random assortment of guys throughout the world.