I know this is probably weird. But, for me, I have to set a "scary" goal in order to force myself into working out and eating healthy. So, I have a goal that by the time I'm 35 I'll be in good enough shape that I'll be able to model underwear (for a place like Target, for example - nothing sketchy). I'm not sure if it's possible to do something like that without an agent or modeling history. But, anyway, having a goal like this helps to motivate me.
I also have a "smaller" (yearly) goal of participating in a couple Triathlons each year. I'm in my fifth year - so, I'm doing well so far.
Bottom line, I find that setting a goal that freaks you out a bit helps to motivate you into actually preparing for it.
I have been riding my bike to charge a power pack for my cell and notebook. If I don't ride then no iPhone or notebook use. It was working good till I got hurt. About one hour on the bike was giving back 2 hours of notebook use. I only was able to use it 2 times before I got hurt. Its now a little hard to ride with pulled muscle. I will start back up after the Doc clears me.
Keeping motivated is probably the hardest aspect about working out for me. Once I get inside the door I'm fine, but I get bored easily and will often cut short or skip workouts. My schedule makes it difficult to find a work out buddy so I often have to go it alone, which makes it even easier to bail out on. I think this site is great for the support and community spirit.