I don't much care for bungies. Even when very tight they allow the load to shift on bumps. Straps are much better, but are a bit pricey.

I use rope. A half dozen or so 1/4" kern mantle in about 7 foot lengths. 6mm x ~2m for the imperially challenged. You need to know a few decent knots. I will often fasten the middle of one rope with a larks head, then bind the load tightly with a Dutchman on each end. A Dutchman will let you apply serious tension and I also like them because they really don't look like they should hold. Google up the mother earth news article on the Dutchman for nice illustrated instructions.