This is my basement gym, a work in progress. You can see all 5 of my DIY projects to date: Plyo Box, Dip Stand, Squat Stands, Modular Kettle Bell (just to the right), and Slide Board (lateral side trainer, big grey thing on the wall).
I spend most of my time working out down here during my off-season, as weight training and cardio cross training are used to build up for my inline speed skating season in the summer. My requirements were to use what I had, build as much as possible, and spend as little as possible. The bike I had, got the trainer stand from Craigslist for $25 (guy moving out of the country needed to get rid of it), bought the weight stand new (cheap at Dick's Sporting Goods, for standard weights), 300 lbs Oly Weight Set was bought used at Play it Again, built the DIY projects listed above, had the standard plates from before (40lbs dumbell set that I added 10 and 25 plates to before swithcing to Oly), and the floor mat was a gift from family for Christmas. Not bad all things considered. DIY and buying used has probably saved me close to $1,000.