Horrible Sound From Under Car

[Riksta]

This one is going to be really hard to explain without you guys actually being able to hear it, but I'll try.

I have this knocking, shaking sound coming from what seems to be the passenger side of my vehicle. It gets worse as the roads get more bumpy, last night I was out driving with a few friends and I seriously thought we were going to be stuck in the middle of nowhere when it started getting really bad.

I was originally thinking something to do with the passenger side front wheel, as when turning right (but not left) there's a clunking sound from that area, but my front seat passenger (as well as my backseat passengers) said they could feel an unusual vibration beneath their feet.

Any idea on what this might be, and approximate costs to fix if it does turn out to be what your ideas are? Its going into the mechanic first thing in the morning so he can have a look at it and let me know what it is and if its safe to drive, but I'm really scared its going to be something fairly major that I might not be able to afford to get fixed straight away :( (read: Falcon comes off road and I drive Colt until I can afford to fix it).

One of my other thoughts was loose exhaust, but the driver's side doesn't seem to be the one clanging and banging around.