As a complete beginner in wood working (unless you count a year of woodshop over a decade ago), I decided that building a cart for the miter saw I just bought would be a great first project. So what did I do with that brand new miter saw? I left it in the box and made all of the cuts with a circular saw. Not sure what I was thinking there...
I mostly followed the excellent plan provided here but used wooden arms to prop up the wings in order to save on cost. I got the idea from the folding sling chair plan. It took quite a few screw ups and adjustments of the lower support bar before getting one of the wings level but I got it eventually.
Update 8/20/13: The miter saw has been a joy to use with the cart and the big flip up wings provide a ton of really convenient work space in addition to stabilizing 8 ft boards for cutting. I added a sliding drawer and some utility hooks for additional storage.