Find a forum or two which you can post in daily and get to know the other people there.
For me, those threads are the "get out of the..." thread and the Beck forum. I poke my head in lots of other places, but I post on those two every day--and that keeps me accountable and motivated and supported and supportive.
There are age groups (20s, 30s...), there are "method" groups (calorie counters, WW, Ideal Protein...), there are exercise groups, etc.
Find yourself a home or two and once you get connected with the posters there you'll have (and be) a cheering section. I find that incredibly motivating and it has gotten me back on track several times when I might otherwise have given up.
Goal: Back to where I was!