All good suggestions above. If you're looking for some other ideas...
Standard aluminum T-Track (popular with woodworkers for hold down fixtures) can be found online for less money than cargo track systems. They also come with all sorts of hardware options. Certainly less heavy duty, but perhaps might work for your application. For example:
http://www.ebay.com/itm/Pair-48-Alu...062694?hash=item237dd677a6:g:0-IAAOSwbwlW~98Y
Make sure to check out the big 2 online retailers (Amazon and Ebay) for cargo track systems. There are some off-brand names, but it all looks like the same stuff to me. Pit Posse?
If you're more into junk-yard stuff... Check out the cargo track systems on top of old Chevy Suburbans, Jeep Cherokees, and my personal favorite... old WD21 square body Nissan Pathfinders. All of them can be used. I like the track systems on the old Pathfinders because they are perfectly flat (no curvature) and can be had with a regular phillips screwdriver. Other track systems are easy to grab though, many of them are torx and torx-security type though, so be prepared when you go. Also might want to bring a hacksaw blade with you in case you need to cut a fastener. Generally they're just held into the roofs of these vehicles with some rivnuts. In any case, like the T-track that woodworkers use, these roof rack track systems probably aren't as heavy duty. But they can certainly be had on the cheap!
If you really want to go old school, then simply some angle iron with a bunch of holes drilled in it on one edge. Secure the other edge to the bed rails with some bolts or rivnuts/bolts and bingo, you're in business. Just make sure the holes are large enough to accept the ratchet strap anchor (duh!) Of course, you do loose some bed width with this option.
Yet another option I've seen is to get yourself some corner anchors from truck beds. Or some door latch anchor points also work well. Both are super strong. Then just drill holes in the bed rail at the appropriate spots and add rivnuts or secure a permanent long backing strip with welded nuts. Then whenever you need a tie down point, just screw in the anchor and you're good to go.