Little River Canyon
Little River Canyon is located just east of Ft Payne and offers 23 miles of scenic riding.  The upper portion of the ride is within the Parkway boundary and the road is in good condition.  The road condition on the lower section of the ride vary widely from good to poor.  This is not a knee draggers paradise and I would not advise fast riding because of the road conditions, but it is a nice scenic ride without too much traffic and the curves and hills will test your riding skills.
The Parkway  (as its name implies) rides along the rim of the canyon.  There are some fantasic views where the altitude drops several hundred feet from the rim to the canyon floor.  These pictures don't do justice to the scenery, but it is very nice.
The upper part of the ride has several purpose built overlooks with picnic tables.  Some of the overlooks are more traveled than others, this one is called Crow's Nest and has very little traffic.

Be advised, the only toilet facilities on the parkway are located at the park above the falls and at the lower end of the parkway boundary, but there are plenty of trees to hide behind.
The falls are one of the most popular spots in the canyon.  The water flow is depends on the rain and the highest flow times are in the early spring.  As you can see, the falls area is a popular place for the kids (the girl in the picture on the left took about 20 minutes of proding before she jumped). 
October 2003 Update -  The road on the upper section has been repaved with a nice smooth asphalt.  I'd still lay back on the speed because of slow cars and because the park rangers don't take kindly to it.  The road on the lower section gets worse and worse.  The county patches the holes but there are so many patches that much of the road looks like it was hit by a cluster bomb.  The park at the south end, Canyon Mouth Park, is going to start charging a gate fee.
** Updates at bottom of page  - Updated September 4, 2006**
July 2005 Update -  Some friends from Mississippi told me that had been over and rode the canyon and really like it.  I asked them if the lower section was still rough and they said it wasn't too bad. I thought that maybe the county had repaved that section...wrong answer.  It is still rough.  Overall the canyon is recovering nicely from the ice storms a few years back.  It is still one of my favorites and I am seeing a lot more motorcycles on the route.  Just wish the county would lay down some new asphalt.
March 2006 Update - I was at the Canyon to try out a new camera and decided to take the ride down to Canyon Mounth Park.  A mile or so into the Dekalb County road that runs from the Parkway down to the Canyon Mouth Park the sign said "Construction Next 8 Miles".   What that meant was they had ripped up the pavement so the road was dirt and gravel.  Fortunately I had taken my all wheel drive Honda CRV because the trip would have been next to impossible on my road bike.  The combination of the road surface and the hills and curves would challenge the best riders.  However, if you happen to be riding a nice lightweight dual sport then the road is for you.  Note - This section of road is NOT the Little River Canyon Parkway, it is the Dekalb County road that leads from the Parkway down towards Canyon Mouth Park.  The Cherokee County section of this road remains intact.
September 2006 Update (courtesy of Randy Brooks) - I live in Ft. Payne and take my '06 boulevard thru the canyon every chance I get. It's a very nice ride. You also mentioned the lower half of the road that leads into Cherokee county as being terrible for cruisers due to repaving efforts. I would like to offer an update the that if I may. As of approximately the middle of July, as I took my son with me on a "joy ride" we decided to go right at the old park location instead of the usual left, which leads to the canyon. Although the county has used tar n' gravel for the road I was very please with its condition.