A router table + router came on sale locally (similar to this one), so I picked it up but hadn't anticipated just how much room it would take up on my workbench. However, my table saw has an extension that was not really doing anything other than allowing me to cut large stock. Luckily (because I didn't measure it in advance), the router table I bought was a good size match, and so I built a frame to house it, discarded the legs that came with the table, and popped it in place. It works like a charm - it made it really easy to make a mallet, for example.
For instructions on how to make the whole thing yourself (e.g. if you already have a router), check out Mathias Wandel's version. Actually, if you haven't seen his site before, do yourself a favor and have a look around - loads of fantastic stuff there.
Step 1: Tools and Materials
If you got this far, doubtless you already own a table saw. For this project, you need a full size one with an extension - mine is the Ridgid R4512, which is probably the most affordable one of this type out there. You will also need a mini router table, of the type intended to be mounted on a workbench. The one I bought came with a fixed base router and all the fittings.
Beyond the table saw, I used a cordless drill, a hand saw, a jigsaw, measuring tape, square, wood glue, 1.5" drywall screws, some clamps and sandpaper. The wood was all offcuts from spruce construction lumber from my woodpile.
Step 2: Measure and Cut Frame
Measure the size of the hole in the table extension and the size of the table. For me, the dimensions were 687 × 370 mm and 605 × 363 mm, respectively. That meant I needed to extend the table by 41 mm at each end, but didn't need to do anything on the sides except provide support. So I made a frame by cutting two long skinny pieces 22 × 38 × 687 mm and two short fat pieces 38 × 41 × 370 mm, and cutting out a rebate at the end of each of the end pieces such that the frame was 44 mm high and the skinny pieces were exactly 18 mm (the thickness of the table top) lower than the fat pieces.
Step 3: Assemble
I glued and screwed the frame together, put it in place and realized I needed to cut a rebate for the switch and slots on each end for the sliding miter gauge. I did the former with a jigsaw and the latter with the table saw, then fixed the frame in place using flat-head screws in the holes that were already there.
Step 4: Done!
Drill holes and drive screws through the frame into the underside of the table to fix it in place (I used 6), and mount your router. The way this is set up I can either use the fence that came with the router or the fence on the table saw if I need to rout a larger workpiece. This router/table setup came with a switch that powers the router, LED lights in the router, and your shopvac if connected. The whole setup works very nicely and it was just a quick job. Great place to put a router table without taking up any more room in your shop - I can still tuck the table saw away under my workbench (see last picture), which is important given my shop is just ~1/3 of a garage.