I consider my digital camera to be one of my most valuable woodworking tools!
For some years I have attended local auctions and have taken many pictures of period furniture. As a result, I now have an extensive library of high resolution detailed digital photos that has proven invaluable. I have learned to take pictures of anything that catches my eye and not to be to deliberate. You can never tell what will come in handy. At first it was a bit embarrassing, but the folks at the auction houses have come to know me and even assist me at times. Knowing my habits, they once gave me a heads up about an exceptionally rare and valuable Boston block front chest of drawers that was on preview. As instructed, I came back 1/2 hour before closing and they helped me w/ unprecedented access to it!
I photograph from all possible angles, pulling drawers out, turning the piece upside down, etc... One trick I have found very useful is to get some poster board, and draw dark, black lines w/ a sharpie on 1" intervals. I put that up next to or behind what I'm photographing. It often eliminates the need for taking measurements or making tracings of curved elements, and I believe it could be used to compensate for lens distortion when scaling from photos, but I haven't used it for that yet.
I purchased a Canon Rebelabout 6 years ago, and the decision to go w/ an SLR proved to be fortuitous. It's capable of taking highly detailed, clear images that allow me to zoom in an incredible amount from my computer to glean details from the photographs. When I was initially pondering what to buy, most people recommended I buy a standard pocket camera. I am delighted I followed my instinct and went for an SLR!
I find a zoom lens to be invaluable, especially when photographing museum pieces where it's not always possible to get close or step back, etc... Photo purists complain that zoom lenses have distortion, but I haven't found that to be much of a problem for what I use the camera for. For "overall" shots, I find the auto-focus to be best, since its reliable and greatly speeds up the process. For detailed macro shots, manual focus is usually the answer.
Since flash photography on furniture w/ shiny varnish finishes usually doesn't yield good results, I've learned to turn the flash off and rely on both small and large tripods. I think a basic SLR camera w/ a zoom lens, and the tripod meets 99% of my needs. Lately I have been thinking about purchasing a mono-pod and a macro-lens. All the other stuff I purchased hasn't proven as useful.
Focus / depth of field has proven to be a most vexing problem. While it's still too early, I think this type of technology will prove invaluable for making documentation photos of furniture in the near future:
https://www.lytro.com/camera
Since digital photos are free, I've taken to documenting everything I build. It's amazing how useful that has proven, as well. I use it both to remind myself and to show others how I solved a particular problem. In one case, these photos unexpectedly because the basis for a SAPFM journal article! When I took the photos I had no such plan to publish them. But a good quality SLR means your photos are really clear, so you do have the option to use them in ways you never intended.
Robert Millard wrote an excellent blog entry on photographing furniture:
http://americanfederalperiod.com/photography%201.html
There was also an excellent article in FWW a couple of years ago on photographing your own work. One of the most useful articles they've published in a long time IMHO!
Whew, I'm rambling. I wrote all this in the hopes that it will help you confirm your decision to purchase an SLR!
JB