Marbled Orb Weaver
http://ento.psu.edu/extension/factsheets/marbled-orbweaver
http://www.spiderzrule.com/orbweaver1.htm
Very beneficial spider around the garden. The "electric" colors help to keep them from becoming prey as those colors are instinctively ingrained in animals and insects as ones typically deemed as hazardous, aka poisonous.
The poor buggers are confused because the weather has been so spring like recently and they think it's time to appear and catch insects. I get them all the time, it's no big deal. By tomorrow, they be gone.
They're like these fellas here:
http://www.hiltonpond.org/thisweek030901.html
Very beneficial but very toxic looking.