Can you please list a few effective (preferably cheap) compact exercise equipment?

TRX : Trx is one of the most universal highly effective pieces of training equipment you can buy period. Can virtually be used anywhere and if you think body weight exercises can't be effective i'd have to say give trx a try. I use it when i'm traveling. In terms of cost, $180 on ebay. If that's too much then check out laird hamiltons fitness programs... Can do everything w/out weights and b effective.