With a tool like Dabbleboard, you can send out the URL to a class so that they can interact from their seat, or get up and write on the board. Plus, with a saved link, you always have an easy artifact not attached to Activ or SMART software. Also embeds.
A collection of templates for popular games that can be used as reviews. Includes Millionaire, Smarter than a 5th Grader and Deal or No Deal. Files are PPT and SMART Notebook.
This simple site is a nice IWB online activity where students can choose letters to spell different words based on objects that they see. I really wish I could embed it, perhaps into an interactive lesson plan, but the little kids K-2, will like it.
I think the most important thing you can do for the little ones is to get them engaged in technology as soon as possible. With the IWB, Little Animation for Kids, has nice interactives and games suited nicely for the IWB.