Are you kidding me? The question is what DON'T we do for winter sports!
I don't know a lot about jeeps and snowmobiles but I know people do a lot of snowmobiling up the Poudre Canyon/Cameron Pass. I love snowshoeing and cross-country skiing and there are a ton of places to do that in nearby Rocky Mountain National Park and the Poudre Canyon/Cameron Pass area. There is a trail guide database available at Snowshoe & Crosscountry Trail Guide | The Coloradoan | coloradoan.com
. These areas are also great for tubing and there is even a tubing hill with tow ropes located not far up Poudre Canyon.
And do I need to mention world-class skiing and snowboarding!?!
Additionally, we have great sporting events located in and around Fort Collins. If you are interested in those, there's a list located here Finally In Fort Collins: Fort Collins - a sport addict's mecca
Hope this is helpful - enjoy.