If you have access to this game by Sunburst software called "Green Globs", use it. One of my more smartass freshmen exclaimed today "I'm learning! I'm learning!", but they were mostly having fun. It's a game that gives you a bunch of globs on a cartesian plane, and you knock out globs by typing in the equations whose graphs intersect them. The more you hit with one graph the higher your score.
I like it because they *need* to know how to write the equations for graphs they want for some other purpose (an artificial purpose, but one to which they are accustomed to submitting)...I haven't run across anything better for clarifying for them positive vs. negative slopes, rise vs. run, how to slide the graph up and down, how to adjust the steepness. I drag it out again when they graph quadratics.
Anyone know of a free version of something like it? I'd love to hear about it.