Get an extra life (10,000+ points) to unlock "Press J for Hard Mode", to start on level 20
Get 1000 pellets to unlock "Press K for Super-Hard Mode", to start on level 30
Get 25 Power Pellets to unlock "Press R for Random Mode", to use different random layouts each time.
Hit your head a lot (you can sit tapping away at the button for a minute or so if you want!) to unlock "Press D to play in the Dark", to play in a very dark set of level.
Get to level 5 to unlock "Press P for Path mode", to open a new gameplay style where you have to try to follow the trail of dots.
