I remember now, it's called dextrin. If there are kids around you can have great fun mixing the powder with a little water and pretending it's snot!
Anyway, Sarma is right, the yellow paper is really good and by far the easiest to use. It has a very thin plastic coating which seals the toner somewhat. I made a good number of boards with it before switching to dry photo resist film. (To try to give some kind of perspective: going from regular paper to the yellow paper is like going from VHS to DVD. Making the switch to photo resist is like going from DVD to Blu-Ray)
Also I got fairly good results putting some old glossy inkjet photo paper through the laser printer, before I discovered the yellow paper. Not as good as the yellow paper, better than hunting around trying to find just the "right" magazine pages