The most obvious way to use a tablet PC is to apply it in the education arena. These days, more and more e-books are being distributed - as a result, that tablet PC of yours can replace those heavy textbooks.
 

Use your tablet PC for education
 

The can also use the tablet PC in a classroom. Instead of having desktops situated in a computer lab, you can have your students bring their own (or the school's) tablet PCs.

You can also use tablet PCs for lesson planning, essentially to store course notes and bring them to class. Alternative uses include grading papers (using the tablet PC's to mark), or even distance learning.

Here's another interesting application - use the tablet PC for retail. If you're a store manager, a tablet PC can replace the forms or notes you used to keep when trying to keep track of inventory. The ease of use of the tablet PC make it easy for any retail personnel to be productive with it very quickly.
 

Your tablet PC is also very useful for customer service
 

Some other interesting uses include operations and customer service. You often sales clerks these days carrying around a tablet PC around to service customers. It also conveys a more professional look than your standard pen and paper.

If you're in the real estate industry, you will very often meet up with buyers and sellers to their home of choice. You might also attend property launches and make marketing literature.

If you use a tablet PC, you can easily get the faces on a particular property (e.g. the price and property tax). You can also post and review classifieds or listings concerning the property.

An interesting idea I heard from a friend is to also create 3D online tours. You can use a tablet PC to stream or show a video of the property's surroundings and rooms.