Try Tradehill they take Dwolla, referral code is in my sig if you want 10% off your trades their for your account. I like bitcoin7, but they're not accepting Dwolla right now. They do take other services however.

I would like to add that bitcoin7 has cheaper per coin prices right now at $15 compared to $17 at Tradehill. I have a bitcoin7 referral code in my sig as well.