Some online companies that I'm aware of:
· CinePost, in Georgia
http://www.posthouse.com
· Debenham Media Group, in Pennsylvania
http://www.3516.com
· Video Conversion Experts, in Arizona
http://www.videoconversionexperts.com
· Wood-land Film Transfer, in Iowa
http://www.wood-land.com
· Todd Video Productions, in Missouri
http://www.toddvideo.com
· Rainbow Pixels, in North Carolina
http://www.rainbowpixels.com
· Videotransfer.com, in Texas
http://www.videotransfer.com
Of all those, the WOODLAND facility looks interesting to me. I've heard some good feedback on them from other people that have used them. If I had a 16mm reel, I'd consider them first on the list.
Be sure to ask specific questions. See what sort of DVD they are using (brand AND media ID). I also suggest film be transferred both to a DV tape (just in case), and a DVD. And find a service that is willing to keep a DVD backup (or file backup on the computer), until they are 100% sure your video is back in your hands. It would be a tragedy to lose a reel (AND the DV/DVD work) or have it damaged in transit, for the return trip.
The advice I give, for sending reels is very simple.
#1 - Only send one reel, as a test, see what they do. Do not trust anybody with your whole collection
#2 - Use FEDEX and only Fedex. I hate UPS, they are sloppy operators, careless delivery men more often than not. The U.S. Postal service, while okay, is not always earnest about verifying delivery. Fedex is. Also, the less time it's in the mail, the less time a delivery service has to make a mistake.