Update 12/3/10 — This chart is already a bit outdated in terms of what the American printers offer! For Europeans, there are two printing services for you to consider, Stoff-Schmei.de (reactive dyes) and Stoff’n (pigments). Hopefully I’ll have an updated chart finished in the next couple months.
Last summer I tested out four digital fabric printing companies by printing the same design with all of them and comparing the results. The post included a comparison chart covering pricing, available basecloths, color matching info, and other details. That chart was sorely in need of an update (mostly due to the introduction of the Spoonflower Marketplace), which I have finally done! Download it here (pdf). And let me know if you catch any errors.