The ponchos are awesome for Spring and rainy days.  The high-end are made by Descente and (I could kick my hiney, but I just saw them at half price from what I bought them).  They're very durable and strong, totally water-proof and have a snug fit so it's comfortable to wear.  You can find them on sale at 
http://www.artechski.com/descente-rain-poncho-black-2313.aspx#.USaXllpMSwcThe mid-quality sports ponchos can be found at REI for less than $40.   
http://www.rei.com/product/743069/outdoor-products-packframe-ponchoThere are also disposable plastic ones that I will tell you, they are worthless.  I bought a pack of 3 and last year, wore one of them in the rain, only to have it ripped to shreds in the wind going down the slopes.  Worst yet, I got it stuck in the chair lift when I exited and couldn't get out.  My foot struck the stop bar and I embarrassed myself as I looked like a novice nerd wearing a poncho.