I have at least 6 broken quests right now and they are starting to add up. I have a murder in Windhelm, a bounty for a boss at Valtheim Keep I killed before the bounty was issued, a bounty for taking out at least 2 bandit leaders from 2 different holds I can' collect on, and a sabre tooth cat to clear from GreyWater Grotto that was already dead when I got there and the quest arrow still is above it's corpse. Fortunately, none of them affect the main story quests yet.

Is there a way to 'reset' them? or at least clear them from my list and glean the reward?

Some of them, although Blood on the Ice (the serial killer in Windhelm) is a http://www.uesp.net/wiki/Skyrim:Blood_on_the_Ice#Bugs. I'm not sure what options are available for radiant quests.

You have to be on the PC I think so you can use console commands.

This is the best Skyrim website, with an excellent search box. http://www.uesp.net/wiki/Skyrim:Skyrim

I forgot to mention, yes, the commands are there to finish broken quests. Just type the quest name in the search box.

If the bodies of the bounty targets have not gotten deleted by the game from the interiors they are in, you might try opening the comsole, clicking on them and type "resurrect" (without the quotes) and hit enter. They should come back to life so you can kill them would be my guess. Worth a try at least.

so...what is the command that I need to enter to FINISH a quest?

You have to identify the quest reference number and the stage of the quest you want to jump to. You should be able to find that info on UESP wiki.

The console command is then: setstage