Originally Posted by Jaywalk3r

Another possible option, depending on your dropout design, is to drill and tap the dropouts for rack eyelets. I did this on my Redline Monocog 29er, which didn't have eyelets for rack or fenders. It worked well, and I've put thousands of loaded miles on it, including a 3200 mile solo tour with camping load. My dropouts (actually track fork ends) are sufficiently beefy that the new eyelets did not dangerously compromise structural integrity.