id'ing ontario inverts?

[rwg]

Does anyone know of a species key or field guide (free online perferred) for Ontario/Canadian/North American invertebrates. In particular I'd be more interested in spiders and centipedes, but anything would help. I have quite an ecosystem in my apartment, and I'd like to positively identify more of them. So far I've got sow bugs (aka pill bugs, wood lice), house centipedes, zebra spiders (very cool) and pseudo-scorpions. I have other centipedes, and several species of spiders I cant nail down yet, and am looking for any resources that might help.

Thanks
Roy