I have a quick question. I have a few of these light switches laying around http://www.homedepot.com/Electrical-Dimmers-Switches-Outlets-Switches/h_d1/N-5yc1vZc33w/R-100058788/h_d2/ProductDisplay?catalogId=10053&langId=-1&storeId=10051 and I am wondering if I can use them to control 12 volts DC, and if so how many amps can I get out of them?
Yes it will work for 12VDC, but switches are often rated differently for DC; both voltage and current ratings may be lower. So if a datasheet for the switch cannot be found, or if it does not specify ratings for DC (which is entirely likely since that switch is only designed for AC), then it's a crap shoot. Your crap shoot, to be exact. If it were me, I'd think a couple-few amps would be OK, but I wouldn't feel comfortable with much more. It may also depend on the load, if the load is very inductive, then ratings could be lower yet, or it may not be advisable to use the switch at all.
Using any device in a situation other than what it was designed for can be disappointing at best and dangerous at worst. If you do not have the ability to analyze the situation yourself, then it would be best to use a component rated for the stresses you intend to expose it to.