The Montgomery County Planning Department has released a very detailed study of statistics for different regions of the county. Details of the report go all the way down the the mundane, such as how much Bethesda/Potomac-area residents have spent at convenience stores in 2009 ($19.5 million, in case you're wondering).
One section I have found to be interesting is pages 29 and 30, listing the "cost of living" in particular areas. This is calculated as the average housing costs plus transportation costs. Silver Spring takes the prize for lowest cost of living, $9,419/year for transportation plus $18,444 per year for housing for a total of $27,863. Compare this to Ashton at $45,741 or Germantown at $36,154 and you quickly see the financial benefit of living in a walkable community with ample public transportation. Wheaton is runner-up for this metric with a total cost of $30,664.
I was unable to find in the report whether housing costs are only rent and mortgage, or whether it also includes other incidentals such as electricity, water, lawn care, household maintenance, etc. If those extras aren't included in this study, I'm sure that suburban, single-family homes would prove to be even more costly.
Also of interest is page 31 which lists Silver Spring and Bethesda as tied for most walkable communities.
Read the full report here (PDF warning)
Update: Apparently Evan and I both caught wind of this report at the same time and we each composed our posts simultaneously and hit "submit" within minutes of each other. Fortunately, we were both focused on entirely different aspects of the report, so we decided to keep both posts here since almost nothing we talk about has overlap. In other words, this is NOT a duplicate post.