I spent my last day of Christmas vacation building a storage shelf for the basement. Its 8' long by 2' deep and 6'6 high. Its made from 14 2x4s and 2 4'x'8 1/2" sheets of OSB. The total material cost was $70 and the only tools required were a saw and a drill. I followed the design laid out by David Wirth in his blog post How to build a shelf for the garage. He has instructional videos and templates / drawings which are really helpful.
The nice thing about the design is the interlocking nature of the screws where the three 2x4s meet at the corners. Each 2x4 is fixed to the other 2x4 by at least 2 screws. The joint seems to be very strong and more than anything adds considerable rigidity to the unit. Each shelf can comfortably take a few hundred pounds. The cut-outs in the OSB to accommodate the vertical posts are a nice touch even if they were annoying to have to chisel out.
This is phase one of operation Basement Workshop which requires that all the junk in the basement gets cleared out and all the good stuff gets organised so that I can make room for a work bench and a small wood shop. I made a head start on the shop by using some old melanin sheets from our kitchen cupboards as a clean back board for storing hand tools. The panels are just temporarily anchored into a pre-existing metal shelving bracket until I figure out a better place for them.