Check out the Harbor Freight, either the local store or the online cataloge. Look for clamps. They have a package of plastic clamps that are hard to beat for the price. They are small but with a firm grip, almost to firm for soft balsa unless you use a scrap of lite ply between the clamp and balsa. They also have some 4" bar clamps at a reasonable price. I just picked up a set of eight for $8 plus tax. Not sure if these "specials" are still on, but they return quite often.

Another good sorce of small clamps is the wood, spring loaded, clothes pins. For long reach, just turn them around on the spring so the long thin ends are the clamp.

Like Bruce said, a sheet of ceiling tile, or a piece of 1/2 drywall board works very well. Ken's magnet system looks very nice, and I build four or five planes a year, but it's Nice but not necessary. A stout flat surface that will not build a twist into your parts is mandatory. I use an old oak computer desk that I picked up in a yard sale some years back. You can dance, if I could dance, on the top and it doesn't move. very strong and it has a 36" x 60 flat surface. Anything you have that is long enough to pin the wing halfs down on, and is not warped is good.

I've picked a lot of great stuff up a yard sales, once I got some solid core doors that were not drilled and I made a bench from them. I left them in my last house when I sold it and have been sorry since.

Bottom line is that there are a lot of inexpensive ways to get your building table ready.

Don