Anyone can master a CD these days. All one needs is a computer and a set of speakers. We can do mastering at A Writer's Room but if the budget allows we recommend sending the final mixes to a real mastering engineer. Why use a real mastering engineer? Let me put it this way. Why use a hand surgeon when you can get by with a GP? I think the answer is obvious. To be specific, a real mastering studio has tuned speakers in a tuned room. This is crucial. It takes the guesswork out of the process. Plus, a dedicated mastering engineer knows all of the tricks of the trade that only come with years of experience. I've used both of the places linked below. Jim Blackwood works for Arizona Public Media at the U of A. Black Dog Mastering is an online joint in Florida, but they do good work at a very reasonable price.
The most important link on this page may be the first one. Here's a quote from the Songwork webpage:
"We are a songwriting education site featuring unlimited access to video lectures by nationally-acclaimed teachers including Steve Seskin, Pat Pattison, Andrea Stolpe, Steve Leslie, Jimmy Kachulis and Bonnie Hayes. The principles covered here can be applied to all genres of songwriting. Learn about story development, song structure, melody writing, prosody, phrasing, point of view and much more. Here at Songwork, we believe when it comes to writing songs, there are no rules - only tools."