When it came time to do the cover art for my novel, I wanted to work with someone locally here in Portland.  I looked at several sources, including Craigslist and web searches, but ended up using elance.  Sorting through the local graphics designers there, MacKenzie Griffith.  McKenzie did a great job, though I must admit the process took quite awhile.  Part of the reason was procrastination on my part.  To do well in this process, you need to have an idea of what you're looking for in a cover before contacting someone.  I really didn't. 

Cover art can cost anywhere from $149 from Bookbaby to several thousand dollars from an established designer.  Some author opt to do the design work themselves.  If you're doing that, make sure that the images you use are in the public domain and make sure that you meet the requirements for both e-books and the print versions.  A good resource for examples for retro cover art is Dave Lewis' blog: Davy Crockett's Almanack.

For me, a professional designer was a necessity.  I probably could have muddled through the ebook cover which are jpegs, but the print versions require conversion to pdf.  I wasn't willing to shell out $650 for a copy of inDesign and take the time to learn the ins and outs of the program.  The requirements for both e-book and print versions are exacting.  It's better to have it done right the first time.

Oh yeah, my novel is now available at Amazon.  How cool is that?