JTG,
Where to stay depends on what you want! If you want to stay near the finish line with 20,000 runners all freaking out and trying to pile into the same restaurants, get on a waiting list and you’ll probably get in. However, if you want, in my opinion, a better, cheaper and more enjoyable experience, then view Boston from a bigger view.
Since, on race morning, you have to get to the bus, and since the busses load at the “T” stop (subway), you can stay ANYWHERE along the T line and get to the bus pickup super easy. This really opens up all of Boston to you.
I’ve stayed in Cambridge cuz I love the college scene around Harvard. You won’t save any money, but you will have an easier time getting into a restaurant. The Sheraton Commander is in Harvard Square, about 100 meters from the T, and goes for under $200 a night.
You could also stay out by Tufts. I stayed at a B and B out there and it was FANTASTIC. About $100 a night.
Last year was the best. I stayed in an apartment in Southie (South Boston). It was $150 a night, but could sleep 6 comfy. It was fully furnished, kitchen, cable, and wireless internet. And it was Southie, which is a really cool part of town (used to be a bit rough, but is now one of those areas that are experiencing a rebirth). The restaurants were fabulous, and I didn’t see another runner the whole week! Race morning I took a cab to the T (it was only a 1/2 mile walk, but I decided not to burn the energy. After the race, hop on the T, ride to the stop, easy half mile home.
Do a search for “Boston Condo Rentals” and all sorts should pop up. I stayed in the condo with a great friend of mine (Oh, it was $150/night and could be split up to 6 ways, although just 2 of us shared it).
If you want the Boston mob scene (which some do) you are asking the wrong guy.
Oh, great running in Southie too.