Solar
(low maint, unattended, low output, expensive, poor in winter)
Wind
(depends on weather, needs open ground or tall tower, works well in combination with solar)
Water
(little access, low but constant power, may need to DIY build)
IC Engine Alternator
(charge batteries on move in van/car/boat, not really renewable but useful if running engine anway, petrol gens may have 12v batt charge output)
Mains Electricity
(strange to include, but may be useful to charge batt & take to off-grid place if required - charger 1/10th battery capacity)
Human
(bike gen, treadle/hand wound - useful for public events or emergencies, gym equipment)