Such as? Anyone?
Overdrive is one such. Smashwords is another. These are two of the first three google hits for "ebook distributor".
Short answer: DRM doesn't work and isn't a good idea. If you want your book to be available on the largest number of reading platforms, but do want some measure of accountability, offer it in multiple non-DRM formats (epub, mobi, pdf) with steganographic watermarking. That's something you can do in-house, like Fictionwise does.
Overdrive is one such. Smashwords is another. These are two of the first three google hits for "ebook distributor".
Short answer: DRM doesn't work and isn't a good idea. If you want your book to be available on the largest number of reading platforms, but do want some measure of accountability, offer it in multiple non-DRM formats (epub, mobi, pdf) with steganographic watermarking. That's something you can do in-house, like Fictionwise does.