If you like to ride a bike and want to see some incredible scenery, I would strongly recommend you take the time to do the rim road of Crater Lake. The ride is approximately 33 miles in length and even though you are traveling around a lake, the elevation gain is approximately 4,000 feet. The good news about the ride, besides the scenery, is the for every foot you ascend, you also get to fly down on descent. Not only do you get to ride the rim at around 7,000 feet above sea level, you also get to hit top speeds of nearly 45 MPH (I am sure you could hit 50 MPH if you really tried, but I think my huge grin killed my aerodynamics).
As far as riding goes, I would recommend a road bike for the trip but many people do it on a mountain bike. I have managed to do this ride a couple of times and we always do it as late as possible. These pictures were taken on October 5, 2003 and as you can see the weather is pefect and the crowds are almost non-existent. We try to start pedaling by 9:00, it is usually a little cool at this time but the ride starts with nice climb.
The recommended ride starts at the Park Headquarters at the base of the mountain. I would strongly recommend starting here as you will end the day on a nice descent to your car. It also has the benefit of starting a nice climb that warms you up until the sun starts to warm the air. When starting from this point you will do a clockwise route around the lake. When you get to the top of your first hill, make sure that you continue past the turn-off a few hundred yards to the parking lot of the lodge, make sure to take a minute and enjoy the view.
Remember that on this ride there are no services once you leave the lodge. Make sure to pack sunscreen and plenty of food and water. On this particular trip we had a sag wagon (my wife, kids, and dog wanted to enjoy the scenery as well) which made life a little easier. There are bathrooms at certain points around the rim. The ride consists of climbs to scenic lookouts and then nice descents. The most important part of the ride (or even car drive if that is all you can do) is to remember to stop and enjoy the scenery. The water is so blue and reflective that you can find yourself staring at the water most of the day. In most of the picutres I have included, you will see a sharp pointy mountain beyond the rim, that is Mount Thielsen. That is a great hike, but more about that some other time...