Frame Sliders - ... I'm thinking Yoshimura.
Me too... get them.
A lower seat - ... Saddlemen?
If you need a lower or more comfortable seat, Saddlemen has a good reputation.
Spools - ...
??? I don't know.
Traffic signal magnet - do these things really work?
I've been researching them and in theory, they should... but there are other things you can do like ensure you maximize your magnetic signal by driving directly over the edge of the traffic detection devices. There is a good link here: http://www.wikihow.com/Trigger-Green-Traffic-Lights
When I have some excess cash, I will buy one.
Fender eliminator - ...
There may be some advantage in the stock fender. For example, it holds reflectors which enhance your night time visibility. It also provides a sort of a rear bumper. I got hit from behind while stopped at a red light and the guy bent up my license plate , pushed my bike forward about 2 feet and hurt my back a little but otherwise I was fine. Without that stock fender, it may have been a little worse on the bike and me. The guy was already stopped behind me and while texting, saw the brake lights turn off on the truck in front of me and apparently in the excitement of his smartphone, forgot there was a motorcycle between him and the truck. He took his foot off the brake on his automatic car and hit me before I moved.
Either way, don't go with a Hotbodies. I had one and took it off because it is junk. Go with Yoshimura if you have to have one.
Integrated LED tail light - . I remember motorcycles with NO turn signals . . . and leaded gasoline . . . and you only wore a helmet if you were planning on jumping school busses...
I remember those days too but roads were less crowded and the only distraction they had was the radio. The turn signals/running lamps out on the sides help a driver estimate your distance and speed, especially at night. I've thought about going cleaner too, but opted instead for safety. Nobody looks cool when they're splattered on asphalt. Never forget that you are approximately 20-30 times as likely to die on your motorcycle as on your car.
Adjustable rearsets - ...
Annodized oil filler cap - Looking cool makes you feel good and these look cool. Don't know how much more I gain with a performance oil filler plug...
Really? If you have excess cash, I could use some.
Racing Exhaust - ...If I go with a post market exhaust like Yoshimura how much weight do I lose?
Not enough to warrant the cost of a muffler. The whole bike weighs 33 lbs. You might lose 1 or 2 on a carbon fiber can but... you could also just eat a salad for a lot less or paint your heat shield like I did. It helps take care of the ugly factor.
Have I forgotton any of the major accessories? A rear rack to mount the plastic milk crate on? A side car? A scabbard for my Winchester '94 carbine? Solid gold performance shifter tip?
Yes, go with the scabbard. Rear rack if it's your grocery getter.
What mods and accessories do you have or think about?
Tank bag so everything you need is right in front of you. I have a Cortech and love it.
Get rim reflectors, LED lighting like underglows or similar, a bright and highly reflective jacket or vest to go over your jacket and the same for your helmet. GPS/smartphone mount? If you don't have ABS, ditch your bike and upgrade.