RepairPal lets you compare specific repair costs for your type of car, in your area.
The site compiles data from 173,000 dealers and independent repair shops to come up with a range of estimates in a given area for specific auto repairs. It also distinguishes between dealership ranges and those of independent shops, which tend to be less expensive.
Testing it I found the prices to be on the high side on what I’ve paid for repairs. The cynic in me believes the RepairPal estimates reflect the inclusion of inflated rates some (many?) people have paid. Because this includes amounts paid by a lot of people who don’t know cars (regular Joes and Janes) it drives up the average. You, on the other hand, could do a lot better.
Having this tool is good in that we’re starting to get quantifiable pricing information, one of the many things the web is good for (this site has some very interesting features).
Once you have an idea of what to expect it’s good to shop around. This is the best way I know of to get a sense of what a repair will cost.