I just went through this with my son, who is now ten months and sleeping really well. I just had to buckle down and let him cry it out. It was hard, because he shares a room with his older sister, but it had to be done, because none of us were getting sleep. Big sister was actually able to sleep through his crying much better than I thought she would. I didn't sleep through it, of course, and it was hard to keep from going in and quieting him, but it was worth it, and after a week or two he was doing much better.
Also, I was nursing him too much during the day. When I talked to my pediatrician about his sleeping issues (he insisted on waking up frequently through the night and nursing), he gave me some info that really helped. If your baby is used to eating every couple hours during the day, he'll want to eat that often at night too. So I focused on feeding him larger solid meals, and nursing less frequently. That, combined with crying it out at night, helped him sleep better. Now he nurses four times a day and sleeps about 8 hours at night.
He also presses up against the bars of the crib in his sleep. He'll wake up with huge red marks on his head from the bars. But it doesn't seem to bother him, so I don't worry about it.