After being a dedicated Pampers user for several years, I discovered cloth diapers and haven't looked back. I didn't really know how easy cloth diapers could be nor how well they could work (in our case better than disposables). You can read about some of my experiences and discoveries with cloth diapers here. I also wrote a quick review for gDiapers here; gDiapers are a hybrid diaper: part cloth and part disposable (and in this case flushable or compostable also).
Now I would like to recommend my favorite places for buying cloth diapers. Jillian's Drawers was where I bought my first cloth diapers. I tried cloth diapers for $10 (no risk, all new diapers) with their Changing Diapers, Changing Minds Program. I would highly recommend this program as well as this store. Their website also gives a thorough description of each diaper and their personal experience with the diaper, which is helpful when you are not familiar with cloth diapers. Jillian's Drawer's customer service is above and beyond, and they are more than willing to answer all the silly questions moms new to cloth diapering have.
I have also purchased diapers from Nicki's Diapers. She has a wonderful selection and offers free shipping on all diaper covers and pocket diapers. Additionally, I really appreciated that her shipping prices for other items are based on actual shipping costs.
Speaking of free shipping, Abby's Lane offers free shipping on ALL items to an address within the U.S. And she ships quickly. Her selection is not quite as big as the others, but she carries the most popular diapers.
I have also purchased cloth diapers from diapers.com, but their selection is limited. Target is now carrying some popular cloth diapers online (bumGenius and Fuzzi Bunz plus others), and I believe in a few select stores. Note: I would definitely recommend Chinese Prefolds or Indian Prefolds over the Gerber diapers sold at Target, although some people do use these successfully.
Occassionally you will find a store that sells cloth diapers locally, but for me (in the midwest) that just wasn't the case. All of the online stores I have listed accept payment with a credit card (types vary) or PayPal. Target doesn't offer PayPal, but does accept gift cards online.
Additionally, amazon.com carries several different types of cloth diapers. If you are interested in purchasing diapers through amazon.com, would you consider starting at my Amazon store, Seasons of Learning. I have picked out the most popular cloth diapers that qualify for Free Super Saver Shipping.