There are some tools that are hard to come by, either they're too expensive, hard to find used, or just not that common for DIY'ers. I've found that Jointers are among those tools.

Fortunately, there's an easy way to turn your tablesaw into a jointer (only a 2.75" wide one, but nonetheless: a jointer.) This involves making a jig that clamps onto a non-straight board while providing a nice straight edge to ride against the fence and produce a single straight edge on the board. Then; you can use the tablesaw as you normally would to produce a board with 2 - or 4 square edges.

This also functions as a taper jig; though it isn't particularly accurate if you're trying to repeat a taper over multiple pieces.

This jig is based on one that's commonly built / available, but the biggest difference between my jig and others is the use of adjustable bar clamps. The toggle clamps used in other jigs don't have a lot of height flexibility, the less expensive ones are not self-adjusting, and regardless of kind, they are still expensive. Check out Steve Ramsey's jig at Woodworking For Mere Mortals for a good video of this type of jig.

TOOLS NEEDED:

Tablesaw
Drill Press & bits
Screwdriver
Wrenches (2)
Clamps
Countersink
Hacksaw

MATERIALS NEEDED:

2 bar clamps, Minimum 6" / Maximum 12" long (Find some cheap ones: Mine were only $7 each. I was looking for some 6" long ones but 12" was as short as they had.)
Misc. Screws
Woodglue
A piece of plywood with a factory edge, at least 24" long
A piece of thinner but sturdy plywood; 3/8" (In the pictures I used Hardboard but this was too flexible; so I replaced it with 3/8" ply.
2 blocks of hardwood (I used maple). Mine are about 3x3x2" but the size will depend on the size of your bar clamps.
2 Bolts, nuts, lockwashers and 4 regular washers

Step 1: Cut Clamp Feet Off & Drill the Base

Cut the bottom (The non-adjustable part) off the clamp.

Drill a hole through the base of the bar, a short distance up from the cut; at the same diameter as the bolts you got. I used 1/4" dia. bolts.

Step 2: Cut Mounting Blocks From the Hardwood

I used a piece of maple to cut mounting blocks for the base of the clamps.

Cut a slot into the blocks to the same width as the bar.

Step 3: Drill the Blocks and Attach the Clamps

I drilled a 1/4" dia. hole in the block in the same position as the hole drilled in the clamp. Ensure that the base edge of the clamp doesn't project beyond the bottom of the block.

Bolt the clamp to the block using the bolt; washers, nut & lockwasher.

Step 4: Cut the Plywood Strips

Cut a strip of the plywood with the factory edge to about 1/8" wider than the width of the blocks. In my case this was about 3".

Cut a wider strip of the thinner plywood (Here I'm using Hardboard but don't use it, it's too floppy) so that it is as least as wide as the width of the first plywood, PLUS the projection of the clamp head. In my case this was 6.25"

Step 5: Glue the Plywood Together & Screw the Blocks On

I glued both pieces of plywood together with woodglue; then countersunk 4 screws to hold each wood block on (total 8 screws). I pre-drilled these holes to avoid splitting the maple blocks.

I also added some short screws (1") between the 3/8" plywood base and the 3/4" plywood strip.

Step 6: Use Your New Jointer!

To use, place a piece of unedged wood on the base piece of plywood. Adjust it so that the portion you want to remove is in a straight line; relative to the factory edge of the 3/4" plywood.

Adjust the bar clamps to clamp the wood down; then set the fence of your tablesaw to remove the minimum amount required to even out the non-square edge.

Adjust the height of the blade to suit, run the wood through keeping the back edge of the guide (the 3/4" plywood) tight to the fence.