Bicycle Racks, Baskets, and other Containers... which ones are good for compact GT?

I have a mid-2000s (circa 2005, but it could be 2004) Timberline GT, multispeed, large size; Timberline says its recent "large" bikes are equivalent to 19 inches (although they use a non-horizontial bar on top of the frame, and thus the seat end of the frame is lower than the handlebar end of the frame). I'm trying to figure out the best way to enhance the bicycle's cargo-carrying capacity. (For the record, it currently has none, unless one dangles a bag from the handlebar or something). Any suggestions would be appreciated.

Also, I have a 2000 Pontiac Grand Prix car and I wonder how it might be rigged to accommodate the bicycle.