Mt. Rainier is a classic ski destination for all skills and times of the year. During the summer and fall it is the go to spot for getting some turns in, or warming up the legs as the snow starts to blanket the mountains. All year you can drive up to 5400' to get easy access into the alpine. In the summer you can ski right off the summit on numerous routes so long as you have the ski mountaineering know-how - or stay lower on the mountain to ski one of the many glaciers which provide excellent corn skiing. In the Mount Rainier National Park you also have access to the Tatoosh that has great skiing with easy access including the growingly popular Zipper Couloir. I would always caution of the weather as getting caught in a white-out can happen quickly and has lead to many accidents and fatalities around in the alpine.
Here are some of the routes I've enjoyed:
Nisqually Chutes: A variation of the muir snowfield that provides a steeper line that tends to stay sheltered and corn up nicely in spring.
Tatoosh: A great little range of summits with many lines ranging in difficulty but with easy access.
Fuhrer Finger: Along with the Emmons route this is one of the more popular and less extreme ski descents off the summit. As with anything on the mountain, they both have their dangers so don't take them lightly.