I have a 3.5 yr old and an 18 month old.....here are some things that we do....
Outside activities - MOPS, church nursery, community pool, Mommy & Me class, library story time, YMCA classes, amusement parks, playdates, Michael's craft store class, bible school, festivals, shopping, arcade, Lowes/home depot activities (a bit young for this), science center, zoo, etc.
Outside- play in yard with outside toys, swim in baby pool, go to park, go for walk
Free Play - play with toys
TV/Movies - videos/dvds= (Baby Einstein, Leap Frog); tv=Sesame Street/Barney
Read Books - read a variety of books - some of which we own, some from the library, some online
Activities/Crafts - watercolor paint, finger paint, color with crayons, playdough, art projects (stamping, glue, etc), cooking/baking, puzzles, board/card games, write/draw with washable markers/aquadoodle/magnadoodle/chalkboard
Napping and eating take up a portion of the day
Learning - work on alphabet, numbers, shapes, colors, animals,
by using activity books, flash cards, internet, etc.
Special toys - Vtech Vsmile; story reader, my first leap pad, read with me dvd,
Dance/Listen to music