My recommendation letters were done using the committee system. Basically, I had three professors write recommendation letters that was sent to the committee. Aside from the rec letters, I had to submit a short application, personal statement, transcript and had an interview, which were used by the committee to draft an overall recommendation letter. If your undergrad school has such a committee, I would strongly encourage you to use it because you get to have sort of a mock interview, and being sponsored by your undergrad college gives you slightly better credentials. Plus, the committe packages the recommendation letters nicely, and sends it out for you in a timely manner. The committee process in my school costs $200, but I thought it was well worth the money.