I looked around on the web for a Lego table for my boyfriend's son. I wasn't too happy with the options. Most were around a hundred bucks. I decided to take matters into my own hands and made a lego table for a whopping $30, and it was rediculously simple to make.
I started off with a Lack side table from Ikea ($9.99), then I got 4 Lego base plates from the local Lego store ($4.99 each, also available here). I just used heavy duty double sided tape I already had to adhere the base plates to the table. Make sure you place some Legos along the seams of the base plates to ensure the grids line up once they're on the table.