After the cost of the paper, ink, printer are all calculated, it's usually cheaper to get prints done at a lab. You could use Mpix, snapfish, winkflash, etc.. They're very affordable and ship right to your door. Of the three I mentioned, Mpix is the most expensive, but provides pro lab quality. If you're a bit more budget conscious, then snapfish and winkflash are good choices. They often have sales, too. I think I just got an email from Winkflash that they're doing 100 4x6 prints for $.04 each
You can upload the images to Walgreens, Cosco, Sam's Club (WalMart), Target etc. from your computer and pick them up at your convenience. Of these, Cosco has the most consistent quality results, because they calibrate their machines frequently (and they allow you to softproof, but that's probably beyond what you want to do right now).
Something else to consider when printing from home, especially if you print off sizes, is that you'll always have wasted paper and ink that adds to the overall expense. Plus, many people conveniently forget to include the cost of the printer itself when calculating the per-print cost of printing at home.
Many inkjet printers are super cheap because they nail you on the ink cartridges. They cartridges don't last long and aren't cheap. Kodak has released a line of affordable printers that are supposed to be the cheapest option for printing at home, but I don't think it's cheaper than using a lab, and the print results aren't as good as a lab.