utne magazine has some suggestions...
free beer/espresso/sweets at the polls
discounts with an "i voted" sticker at cafes/bakeries/etc. on election day
fines for non-voters (works in australia-95% vote!!)
tax break for voters
free lottery tickets to a national lottery
make election day on a weekend
while most of these would be tough to make happen, we all know some shopowners to suggest discounts to, and anyone involved in their community could set in motion a plan to offer baked goods, etc. at the polls. or marble magnets