POD printing is best for a small quantity of books--under 2,000 units. A business that takes on print on demand, or "short-run" orders will print your book digitally rather than traditional offset printing methods.
Websites such as Lulu.com or Comixpress.com allow you to send in digital files and specify the amount of books you'd like to print. Many traditional printers also will take on POD orders--check to see if a local printer will handle the job.
Web-based POD printers often allow you to sell your work through their websites--a valid consideration if you hope to reach a wider audience or recoup some of your printing expense. Get several quotes from various printers to ensure you get the most for your money.