Welcome to MTR, momof3.
All cell phones have a monthly fee (except for prepaid phones, but you still have to add money to those regularly). All Blackberries are cell phones, but there are indeed many other types of devices with WiFi, which can access the Internet when they are in a hotspot.
In fact, there is an almost limitless selection available of different products that include WiFi - for example, the Archos 7 (which we recently reviewed), laptop computers, netbooks, HP iPaqs, and even the Sony PSP, to name a few. One product you might be interested in is the iPod touch, which is basically an iPhone without the phone. It doesn't require any monthly fees and it does have WiFi, so it can access e-mail when it's in a hotspot. It has a calendar you can sync with your computer as well, although its calendar is not as feature-packed as the calendars on some devices targeted more specifically toward organization and productivity (like the iPaqs).