Trails.com does a nice job mapping out the various bike friendly trails around the country, including those in Minnesota. This helped me discover more trails than I knew were within an easy drive of Minneapolis. MNTrails.com is another good sources for trail info, although they list fewer trails as of this writing.
Registration (and in some cases, paid registration) is required to access detailed info or topo maps. However, once you have a trail’s name, you can normally throw that into Google to find a free source of trail info such as a dedicated website to that particular trail.
On Saturday, I checked out the Lake Wobegon Trail starting in St. Joseph, MN. That trail is around 75 minutes from Minneapolis, in great shape, and had very low bike traffic for a beautiful Saturday afternoon. I highly recommend it.