Inside scoop from a former resident (I'll skip the snide rejoinders about regional parochialism):
The Idaho Falls, ID airport is served by Skywest/Delta out of SLC, Alaska/Horizon [best darn regional airline in the US: free microbrews in flight!] out of Boise, Northwest out of MPLS, and as of Fall '05 Allegiant direct from Las Vegas (promo fares). It's about a 1.5 hr drive to Jackson Hole, as someone said, and not a bad drive if you know what you're doing on winter roads. There's also a shuttle from IF to Jackson, RT $70 <http://www.jacksonholealltrans.com/expressschedule.html
Targhee has more reliable snow, esp. this time of year, and is a shorter drive from Idaho Falls.
If you're in IF long enough to have time for dinner, try Rutabaga's (208.529.3990) on the river for well-prepared bistro fare, & say hello to Wes & Scott. Tell them Deborah sent you!