As I was preparing to glue the two boards together for the bottom of the DVD shelf, I got a little nervous about such a wide board with only glue to hold it together in the middle (even though I know the glue joint is usually stronger than the wood itself, bla bla bla), so I decided to reinforce it with some biscuits. I considered making some biscuits (or would they be splines if I made them myself?), but decided I wanted the expansion properties of commercial biscuits. I bought a bag at Ace, measured the thickness, and chose a 3/16 slot would be close enough to the standard 4mm of a biscuit cutter. After jointing up the two mating edges (with the boards clamped together in my vise), I set my plow to cut a groove down the center of the boards, and referenced off of the face edges to make sure everything was consistent. I made sure to stay a couple inches in from the finished length of the board.
Because I wasn't cutting all the way from end to end of the board, my plane cut an arc-like groove, and couldn't reach the full depth even in the center of the groove. I took my 3/16 mortise chisel and deepened the groove appropriately, checking to be sure my biscuits would sit approximately halfway in the groove.
After a test fit, I loosely filled the groove with a handful of biscuits and plenty of glue, and clamped up with the two clamps I have that are long enough. Hope it's enough! I'm not really too worried. Once the glue is set overnight, I'll crosscut, shoot, and start laying out for dovetails.