Look at Rep fitness. They have all sorts of attachments and ability to build whatever you want through a very modular set of parts you can buy.
I would have added one of their pulley systems to my rack, but I had already found a nice functional trainer off of craigslist.
I'm sure Rogue has similar stuff available - but I find their prices and shipping a bit higher without really anything being better. OK, I take that back - I LOVE their Monster weight storage pins (they fit on my Rep 5000 series rack).