Jo-Ann Fabrics will have the foam you want for the rail. For the center padding, you'll need some foam I can't remember the specific type of right now (high density?), or carpet padding will work as well. While you're at Jo-Ann's, you can pick up the fabric you need too. You'll be looking for Velveteen, but you can also use poplin. Take some cards along with you to test the "slide" of the fabric you're gonna use. Wal-Mart often has SUPER good deals on poplin as well as fistfuls of other fabrics that "slide" just fine.
Check out the following sites:
http://www.scottkeen.com/forum/http://www.pcpotato.com/poker/http://www.homepokertourney.com/Scott Keen's site will have all kinds of different solutions for you for cheap. The carpet padding is prolly the cheapest solution to the center padding, and the poplin is prolly the cheapest fabric - "official" type speedcloth will most likely run you about double the cost of poplin or Velveteen. Jo-Ann's and Wal-Mart should both carry the vinyl for the speed rail, Wal-Mart having less color selection but lower cost in my area. Look for Whisper or Marina (I think those were the two better choices for vinyl) for the vinyl.
Oh, and get yourself an electric staple gun. Don't argue with me, just shut yer yapper and do it. It'll cost you $20 but that money will allow you to use your hand the day after you finish doing the rail.