The Ferber method worked for us.
http://www.amazon.com/Solve-Your-Childs-Sleep-Problems/dp...
If you don't want to buy the book, it basically says take the bottle away all at once. Go through your normal bedtime routine, but put him to bed without the bottle. He will cry and that's expected. Leave his room, then go check on him at increasing intervals. For example, check on him after 5 minutes. Don't do much talking, you can say it's time for bed or something quick like that, then tuck him in and leave. Sometimes my daughter wouldn't lay back down, so I would just tell her good night and then leave. Then if he keeps crying (which he probably will) then wait 7 minutes before you check on him the next time. Then wait 10 minutes. There is a whole schedule in the book to follow, but you could easily do your own times.
The first night we did this with our daughter she cried for an hour flat. We took turns going into her room. The next night she cried 30 minutes. It took about a week and then she just went to bed without a bottle and without crying. Amazing.
By the way, we did it at 18 months too so don't let people get you down.