This was SO easy to do. We got our patio furniture really cheap years ago on clearance and it has actually held up remarkably well. We very rarely use the patio table though. It's usually pushed off to the side next to the screen where it gets pretty dirty. I was thinking about getting rid of it for more play space for the kids, but decided to turn it into a chalkboard table. The best part it was less than $10.
It is just an old glass table. Not the most beautiful of tables.
What you need:
Chalkboard Paint (I got a small can for less than $4 at Walmart)
I already had a paint roller, but I did send my hubby out for one that said smooth or for a foam roller. I actually used both and they worked similarly. I had a pan for the paint and roller, but it was easier to just pour the paint on the table and spread it out. I painted the top as even as I could, rolled around the sides, and let it dry. The paint can says two coats and I put on three. After it has dried for a couple days (the official time is on the can), you rub chalk all over it to condition it and it's good to go. I was worried about the paint staying on a glass table while being outdoors (well in a screened porch), but it's been a couple months and looks fine. I figure if it does wear off I can pressure wash it or scrape it off and start over.
My kids love it! They've spent lots of time drawing and writing on it. Sissy practices her letters and drawing. Bubby likes to draw and bang the chalk on it for a nice effect. He has only eaten a little bit of the chalk. :-) Their cousins and friends love it too. Our neighbo'rs daughter helped a little bit in the chalk eating too. Good thing it's not toxic.
One of our teachers bought some of the magnetic paint and spent time painting different things around her classroom to make them magnetic. Now I have the urge to paint with magnetic paint...somewhere.