How do I find roommates in the Boston area?

[Julie]

One of my friends and I are interested in renting a 4 bedroom apartment, after finding two other females to split it with us. We are interested in the Boston/Allston/Brighton/Cambridge/Somerville area...

I've posted a listing for roommates on craigslist and on facebook without much success. What are some good websites/resources where I can try to find 1 or 2 female roommates to live with us?

Thanks in advance!

(Only serious suggestions, please!)
Unfortunately, I'm not a college student anymore. My friend and I both graduated this spring. Therefore, we probably would prefer living with young professionals over students.