I need to get from Houston to Toronto in June. Any ideas of a way to do it for less than $500 airfare?

Amtrak. It appears the train will cost at least $310 without discounts.

I'd spend some time on sites like kayak.com. And you might get better feedback posting this on the Airlines forum.

If you have the time thursdaysd is correct. Only ride the train to Buffalo, NY and then get a bus to Toronto since the Amtrak train gets into Buffalo at 9AM and the train to Toronto is not until about 3PM. Make sure you have your passport valid for 6 months after you enter Canada. Are you coming back to Texas?
The cheapest good place to stay in Toronto is the HI Hostel. The other hostels are really bad.

jetblue.com HOU NYC BUF from $200 one way

cross to Toronto cheaply bus probably cheapest

other deals cheapoair.com

you might fly to NYC take the MapleLeaf train up

a very nice ride

greyhound.com Buffalo to Toronto $20 3 hours