Personally I think the chocolate lollipop with a pretty ribbon and a tag saying thanks for coming to my party is sufficient for a 1-yr old's party. (I did packages of M&M's for my first DD's first.) I am not a fan of all those cheapo little toys and cr*p from the dollar stores and birthday places - my kids have tons of toys, and the last thing I need in the house is more little junky stuff (plus then I have to worry about safety, keeping them all away from my 5-month old, none of them are rated for under 3 years, generally.) If you go that direction, think of stickers or tattoos, something that is consumable and will be used up easily. You can get a sheet of stickers or tattoos for each kid, these are best for ages 2 and up.
I like the beachball idea someone else mentioned, or you can print out some coloring pages and staple them together to make a mini coloring book - maybe make a cover page that says "Thanks for coming to my birthday party!" (I did that and bookmarks for my 4yo DD's birthday party last month - her party theme was the book Very Hungry Caterpillar, so I got a bunch of caterpillar and butterfly coloring pages and activity sheets free from the internet.)
Here's the link to the Disney Playhouse site - you can get MM printables from there:
http://atv.disney.go.com/playhouse/printables/index.html
If you want you can also add some little packs of crayons -Crayola has a ton of specialty crayons, get the younger kids the washable ones and get the older kids the glitter colors or neon ones.
HTH
Have fun and good luck!