I recommend http://www.payyourrent.com
because they process payments faster than any of the others out there. If you pay before 4pm eastern time your landlord gets the money in your account the next business day! I use to hate wondering when my check will be deposited and I don't have to do that anymore. Also, a live person always answers the phone any time I've ever had a question about my accounts or properties and they act like real people rather than robots at some call centers. Very cool company.