In the "Don't Vote" corner: Russell Brand. In the "Do Vote" corner: Armando Iannucci, who argues that, at a time when everything seems uncertain and unstable, exercising your democratic right could make a crucial difference rather than a negligible impact.
Personally speaking I, like Iannucci, can understand Brand's arguments, and indeed have sympathised with that gloomy and cynical attitude in the past. However, though I remain jaded by mainstream politics, I will nevertheless be voting in May, having been enthused by the Greens - both by their status as a genuine alternative on the left (Labour and the Lib Dems? Don't make me laugh...) and by a rapidly growing supporter base that suggests significant electoral success could become a reality rather than merely a pipe dream.
If you're unsure which way you should go, Vote For Policies is, as ever, an invaluable resource.
(Thanks to Jimmy for the first link.)