I'm pretty sure that if you've saved up the cash to buy yourself a PS3 then you're going to want the whole experience, and thus you'll want a DualShock SIXAXIS controller. However, if you don't feel like ponying up another $70 just to get that rumbling sensation (which should have been in all of the controllers to begin with) you have another option. Albeit a strange one.
Of course, by strange I do mean, big, ugly and unappealing. So much for my grace and tact. The small black thing you see on the left actually clips onto the bottom of your SIXAXIS controller, and provides you with the wonderful vibration that your hands have sorely missed. The other small box (with the huge antenna) plugs into one of the USB ports on your PS3.
Sure, when you hook this up it will make both your controller and console look completely ridiculous, but it's not all bad. You get an FM tuner, which I'm sure someone might find interesting, were this the mid-90's. The only real upside is that it only costs around $18 bucks. Personally, I wouldn't waste my hard-earned cash on one.