Consider a portal of related records where each option selected is a different record in the portal.
Or this can be done from a list view based on that same table.
Your relationships might look like this:
People::__pkPeopleId = People_Item::_fkPeopleId
Items::__pkItemID = People_Item::_fkItemID
Items would be a table of your "100 items of interest" with 1 record for each item of interest. People_Item would record each person's selected items of interest--one record linkis one people record to 1 item record. You can design your People layout to include a portal to People_Item for recording the user's selected items of interest.
With scripting and conditional formatting, it's also possible to set up a portal so that it looks likce a set of check boxes but clicking a check box adds/delete a record from People_Item. This then gives you your "check box" interface but you can chart the data from People_Item.