I would go to your local pawn shop. They usually have some decent floor standing speakers. And they usually don't know how to price them so you can get good deals on them. Receivers too. I got some Infinity Primus 250s for $100 and a receiver given to me by my uncle.
Another, probably unpopular choice around here, is soundbars. Vizio's soundbar w/o the subwoofer is only $100 and is pretty decent. It's kind of muddy, but not the worst I've heard. I currently have a Samsung HW-D450, and I quite enjoy it. The only downfall is it only has one analog input, two digital (optical) inputs, and no outputs.
Another pair of cheap speakers I was impressed by is the M-Audio Studiophile AV40.
The pawn shop suggestion is a good idea but test the gear (OP) first before laying down the green. Look for rips and tears in the speakers cones, rattling of the cabs (by wrapping the enclosures with your knuckles, any rattles from the baffle pass on them), rot around the speaker surrounds (cuts nicks etc). test for proper balance between L/R speakers (checking to make sure all drivers function in their freq ranges). Good deals can be had from the local used shop, sometimes really great deals if you are lucky.
DIY speaker kits are another economical way to get good sound for not a lot of money. See Partsexpress for examples of complete kits that perform well and are beginner (DIY wise) friendly.