Consider riding a gear high. It makes you less likely to spin the tire when accelerating and creates less engine braking. Be a little less aggressive on the throttle than you normally are and use a little less lean angle (that means a little less speed through the corners).

Try to ride in another car's tire path - there will be less water build up there and more traction. Try to avoid the middle of the lane where oil builds up. Be very careful during the first hour of rain... very slick everywhere because the fresh rain will bring oils to the surface of the road as well as wash away built up rubber.

The other thing is that your ability to see the road surface conditions will be degraded. There's still a lot of sand out there so you've got to allow for that. Depending on how hard it's coming down when you ride, your visibility to drivers may also be degraded. Give 'em more room.

The key here is smoothness, and for that you have to be relaxed but stay attentive. So take all the tips from this FAQ, and be aware of danger areas. But DON'T get frightened and tense up. It's counterproductive. The key to riding safely and even (as some people report) enjoying rain riding is to get comfortable and relax.

Wet Weather Braking
If on your ride home you ride for a ways without using the brakes, periodically drag them gently a little to squeegee the water off before you need to use them. If you don't "clean" them like that, you'll squeeze and get almost no braking, react by squeezing harder just as the water cleans off, and risk locking the wheel. You can get a feel for how often you need to do it depending on rain and splash intensity. If you get splashed from the side by a car, "clean" your brakes right away. I tend to use a little more rear brake than in the dry, and cover your clutch more.

Rain Riding Hazards

• Stay away from anything metal or be extremely careful when crossing. Road-work plates especially, but also manhole covers and bridge expansion joints. Especially set up your line through corners to avoid them.
• Fallen leaves. Not an issue all times of year, but in the Fall, woah, baby, watch out. Even slipperier than metal.
• Especially be careful on the WIDE paint lines. If you are turning in an intersection, you have to cross four lines while leaned over. I've never fallen, but sliding the front tire like that is needless wear 'n tear on the heart and brain.
• Stay away from big trucks if you can: 18 wheels splash a lot of water...I mean a lot!
• Be careful at intersections where cars stop and drip oil, especially when it first starts to rain. Tollbooths are particularly bad. Also, when it stops raining those same areas, where the road is depressed from heavy car traffic, the last water runs off of the greasy areas it settles in these depressions and leaves the grease and oil behind when it evaporates.
• Beware the V-gutters that connect curb gutters across intersections. In heavy rains these can become completely submerged and can catch you by surprise. Also beware of the area in the road where the gutters
  drain into a scupper under the sidewalk. On a well constructed road the grade will direct water towards the scupper and the surface water on the road will be deeper in that area.
• In very heavy rain watch for flooded exit ramps: let the water slow you down, keep the clutch in and rev your engine so no water gets in your pipes.

Staying Dry
If your butt and hands are getting soaking wet, this also detracts from the enjoyment and can become a safety issue if you become distracted.
Gear, gear, gear...

The Bargain Approach: If you're not worried about looks, etc, and don't want to spend lots of $$, keep a 50 gallon trash bag and a roll of duc tape at the office. Poke holes in the trash bag for your head and hands and duc tape the bag around you (be sure to leave enough slack in areas where there's a lot of movement, but tape all baggy parts up so they don't get caught on
anything). Be sure to NOT sit on the bag on the seat or you'll be slipping and
sliding in the saddle!

If you happen to have snowboarding gear (most of it is waterproof), wear that. I used to wear 'boarding pants and a ski jacket atop my leathers in the winter.

If you already have decent riding pants/jacket, and/or are on a budget, Frog Toggs make a good slip-on rainsuit that works well & compacts nicely. Top & bottom set for $60-ish.

Aerostitch: In serious rain, the Roadcrafter suit is good but not 100%, especially on a nekkid bike like a Monster. You will be fine in light to moderate rain, intermittent showers or a light steady rain, but a moderate steady rain or downpour will first soak your crotch and then the rest of you. If you plan on riding all day through the rain, you will need a dedicated rainsuit. For commuting, however, an aerostitch can't be beat, especially in hi-viz yellow.

The Darien line (2 piece) is in my experience damn near impervious to rain, which is it's purpose in life. Goretex, tape backing all seams, etc, etc. It's totally awesome. About $300, but worth it. I have just the Darien pants, and rode through some pretty insane weather since I've had them, and didn't observe a drop making its way through.

Faceshields
Face shield fogging. Especially in colder weather, it gets to be a real issue. Fog City face shield inserts are highly recommended! Don't mess with the Fog-X stuff.

Face shield water buildup. Try polishing the outside of your faceshield with some auto wax (carnauba). That way the rain will bead up and off. You can also turn your head to clear the droplets. Rain-X is specifically not recommended for faceshields as it reportedly can cause delamination of the plastic. (Some members do use it, or the Rain-X wipes, however and have not had any problems. YMMV) Some gloves also come with a little squeege built into the index finger, but this in itself probably isn't enough to do the job.

Lastly...
Most of the riders who responded said that once you get used to rain it becomes no big deal, and may even become fun.