What players are available vary a little depending on what country you are in but there are plenty of cheap ones available. Just look for ones that say they are multiformat. I would just try googling "multiformat dvd player" just to get an idea of what is avalable, maybe call a few local stores and ask what they carry if you want to buy locally. You can look up both reviews and info on what they can play here.
http://www.videohelp.com/dvdplayers
there are 894 listed that can play dvd-/+r and can play divx and or xvid. Some are only available in some countries though.
http://www.videohelp.com/dvdplayers?...Submit2=Search
IF you want to go really cheap, you might want to look for a jsi player if you can find one. They kind of have a reputation for playing anything. I got mine for about 35$ on clearance (not one of the models listed on video help) and it will play anything you throw at it including
nero digital (model js5113, I think it is discontinued though). It also has a usb port for viewing pictures, but I found that it will play anything from a usb hard drive as long as the files are in the root directory (no subdirectories) and it is formated fat32.