I'll "third" the recommendation for Blurb, but I'll also say that it's the only one I've tried. I recently published two books with them and been very pleased with the results.
I will say that Blurb was attractive to me because I've had some history in publishing - I wanted to be able to use my previous experience with Adobe InDesign to lay out my books, so their ability to accept a PDF was a deciding factor for me. I downloaded their InDesign plugin (which really only automates the initial document layout by providing dimensions and a non-printing set of guides which help define bleed lines and trim lines and such), as well as their ICC profile for Photoshop.
You didn't ask, and you may have this information already, but here's what I did to try to ensure a quality outcome. Your mileage may vary, and I'm open to suggestions from others about improvements...
1. Because this was my beginning foray into publishing, I bought a new monitor (Asus ProArt monitor) and a Spyder colorimeter (Spyder Pro 3, I think). Spyder's got some great tutorial videos on how to calibrate monitors, and I've been really pleased with the simplicity of the tool.
2. I do my initial image processing in Lightroom, primarily again because of the simplicity. I've found I get most images about 95-98% of the way to where I want them in Lightroom. I export the finished files from Lightroom as RGB TIFFS, cropped, but unresized from the original RAW resolution.
3. I bring the TIFFS into Photoshop and do any additional processing (specific alterations, adjustment layers and such). Soft proof the images using the Blurb ICC profile. Resize the images to final dimensions and DPI (Blurb wants the files at 240 dpi, iirc). Then permanently apply the Blurb ICC profile (this converts the image to CMYK) and save as TIFF.
4. Import the images into InDesign as part of the book layout process. At the conclusion of this phase, I used the Blurb presets (this is part of the downloadable addon for InDesign) to export the PDF, and then shipped it to Blurb. A few days later, presto, books appeared. My experience was that they always arrived a day or two before the website suggested they'd arrive, which was nice.
A couple of additional notes:
- You can purchase a swatch kit of papers from Blurb for their "pro" papers. It's $7, and it gets refunded on your first order. I did this, and was pleased - it helped me pick the paper I wanted. Initially I'd intended to use their heaviest, most expensive paper, but found that I didn't care for it quite as much as I expected - the "2nd best" paper actually appealed to me more, and in my books, that judgement held up.
- I only printed hard cover books with slipcovers, so can't speak to the other options. My impression is that the slipcover printing is a bit more variable than the interior printing. On one project I did two sizes (8x10 and 11x14) - the slipcover on the 11x14 was spot-on, but the 8x10 were a little less so, but the interior work seemed to be of the same consistency. My understanding is that Blurb actually has a number of publishing houses working behind the scenes on their website, so it may be that I just was seeing the difference between one house and another (because of how I ordered, the 11x14 came out of an East Coast location, while the 8x10s came from a Seattle location).
- If you're printing a lot of copies of a book, the only way to get a proof copy is to buy one book first, evaluate it, then make corrections and upload new PDFs, if necessary. On one project, I did this - my proof suggested that I needed to correct 3 images (out of about 90), and when I reuploaded and got the "final" order, I was pleased to see that those new 3 images had improved, while the other images had stayed as I'd expected. This made me trust my workflow, and Blurb's consistency. It's a little difficult to swallow that there's no other way to make proofs other than to buy one full-price copy, but at least in my case, it was worth it.
- Lastly, if you're producing solely B&W material, Blurb's system may not be the solution for you. Blurb can only accept color (CMYK) TIFFS because their digital presses are a six-color process, so even if you're working with black and white images, the files still have to be color. Only because I've had some experience with offset presses where can run true half-tone images, there were several B&W images in my books where I felt I could see a slight greenish color-cast to the blacks that wouldn't be seen using other printing methods. The color shift was so slight that I chalked it up to me being super-picky - it didn't prevent me from using the final product.
- You can pay to have Blurb remove their logo from a last page they automatically add to your PDF. I didn't. It was understated enough that I wasn't bothered by it. YMMV.
Good luck with your project. I'll admit, my foray into the new (to me) world of one-off or short-run digital printing has been really quite eye-opening. A few years ago I dreamed of printing books with an equivalent quality to some of the Ansel Adams books that were in my dad's library. I don't think Blurb's quality is quite there yet (see my comments about the B&W images), but it's pretty damn close. It's a really remarkable world we're living in, where that level of quality is available to the dabblers and advanced-amateurs like us (or me, at least...)