There is plenty to see and do in Anchorage in 6 hours.
If your layover here is in the morning/afternoon the Sat. Market on the park strip at 9th ave. would be a grand idea, as would a trip to the Alaska Museum of Natural History
http://www.alaskamuseum.org/
or have a cabbie drop you off Downtown (less then 15 min from the Airport)
on 5th ave. for a few hours of outdoor shopping fun.
While downtown indulge in fine dining at
Simon & Seafort's Saloon & Grill
http://www.fodors.com/miniguides/mg...chorage@11&cur_section=din&property_id=365080
Right now the weather is in the 60's and sunny and hopefully will be even nicer a couple weeks from now, have a fun quick visit.