if ur going to be riding it predominantly on road/bitumen with very occasional use on trails, then a hybrid will be fine as most hybrids come with tyres that enough tread on em to ride on gravel. otherwise, you can get like a "lower end" mtb that will still be durable for trail riding, yet the design of the frame angles will still be slack enough to ride in and around town. as noss said, anywhere between $400-500 would be fine, but (as with everything.... usually!) the more you pay, the better components the bike will have and thus last u longer and require less servicing.
ahhh.... a suspension seat post might be worth considering if ur just gonna use it as a recreational thing and only really gonna ride paved bike paths in and around the city. Bike brands worth lookin at are Giant (usually their bikes r good value for money, they've been in the market for AGES and only sell quality stuff), GT (cos i like their "triple triangle" design frames and are also pretty good value), Trek and Advanti are also worth considering.... probably stay away from Norco as they mainly focus on "North Shore" style riding and won't really be worth considering for what u wanna ride for.
anywho, u're probably getting bored now, as tas and noss have said, check out you local bike shop and they should let u ride a few that interest u. if u need a helmet and lights, most bike shops should be able to giv u some sort of deal with them, or even chuck em in for free! (as me mate got - lucky bastard!).
good luck with it man, if u hav any more qu's, just ask away as i LOVE cycling stuff - esp mtb'ing!