Letting kids LIVE - seriously an awesome list of easy things for kids. about 100 things for a 1-3yo child to do!
'100 Ways to entertain a toddler'. This Mom has fun (and funny) ideas to interest her toddler. She rates each with a grade to it's success. Good reference.
Indoor ring toss!
Baby sensory bag
The Stay-at-Home-Mom Survival Guide: Infant Activities (best list I've seen)
101 Things to do with Your Toddler
Infant Brain Stimulation: How playing with your baby makes her smart: "6 to 12 Months
HUGE list of activities for ages 1-4.