This is my H shifter that I made from a gamepad found at EBGames.com. It has a bunch of buttons as well as analog sticks. Each "gear" is simply the shifter keeping a button depressed. It's a "Dual shock" pad, meaning it has vibration force feedback, so I decided to leave the two vibration motors in, but I haven't gotten around to loading the special drivers that activate force effects. The shifter knob is the stock knob from my SE-R.
The shifter mechanics is made from an old gameport joystick. I used the bottom half of the joystick base and the ball/stick assembly. There is a section of threaded rod epoxied to the joystick stick, and the shifter knob is simply screwed into the rod. The shift gates is made out of a piece of 1/8 inch acrylic. I drew up the gates on the paper masking that comes with the acrylic, and cut it out (very slowly) with a dremel. The shift stick slides into each gates and depresses a button mounted under the gated acrylic. The buttons are just some normally open pushbutton switches that I had lying around.
I'm using the H-shifter in conjuction with a Logitech Wingman Formula Force Wheel (old red cable driven one). I'm also using a Thrustmaster Nascar Super Sport gameport wheel and pedal set. Yes I'm using two wheel and pedal sets. Well actually, I'm using the Logitech Wheel, the thrustmaster pedals for gas/brake, and the logitech gas pedal as a clutch. It'd be pretty pointless to use a gated shifter without a clutch. I still need to figure out a better clamping system. The current 3inch C clamp isn't very stable.
With the shifter I usually play Live for Speed.