You could also use this Google Drawing to have students make a digital pizza. They'll drag 100 ingredients onto the pizza. Click the image to make a copy that you can use.
The kindergartners enjoyed this video about Counting to 100 by JoJo's Circus.
We also played "Guess My Number" using the free app Counting Board on our iPads. You can use this app to have students play any game you typically play on a 100 board. They love this app, and once they learned a few different games to play on it, they would sometimes pair up on their own with one student being the "teacher" and the other being the "guesser" and play! Teach them to take screenshots of their work, and they can post to Seesaw and use the typing and microphone tools to explain their work. (Have I mentioned lately how much I love Seesaw?)
Another tool I loved to use for teaching number concepts is the interactive 100 chart from abcya.com. We would often project this to our interactive whiteboard and play Guess My Number and other hundred chart games using our interactive board. Abcya.com has some other fun 100 day games, as well. I've listed those below.
If you haven't before, this would be a great time to check out the Unite for Literacy site. Tons of great free books, like this one:
If you've got awesome 100th Day ideas, please email me some pictures or share your ideas in the comments below! Happy 100th Day!