As far as I know Sticky Maggots are essentially a ball of maggots stuck together in a similar way to a ball of groundbait. The link in Dave's reply suggests various ways of getting them to stick together (with Horlicks being one of the most popular suggestions).
You end up with a nice, tempting ball of smelly maggots sitting on the deck for the fish to attack, rather than single maggots drifting slowly down to the bottom.
Sticky mag comes into its own at the right venue.Its just finding the right venue at the right time.(a bit like anywhere really)
Ive put 4 maggots on one hook and then done the sticky routine around them for Carp and had some really good results