Below are two TI-Nspire documents from Spencer Williams that show visually the operations of adding and subtracting fractions. There is also a pdf file to support the use of these in the classroom. Thanks, Spencer, for sharing these.

Ancient Egyptians knew fractions like 1/2 or 1/4 ((one piece of a pie).
But to make fractions like 3/4, they had to add pieces of pies like 1/2 + 1/4 = 3/4.

For some reason, they never repeated the same fraction when adding; ie they never wrote: 1/4 + 1/4 + 1/4 = 3/4

This website presents a range of Egyptian maths problems for you to solve. Good luck!

http://www.mathcats.com/explore/oldegyptianfractions.html

To play this one-person game well, students need to work with equivalent fractions, and be able to add and subtract fractions. Don't forget to turn the sound on!
http://illuminations.nctm.org/ActivityDetail.aspx?ID=18

Here is a neat two-person version of the game.
http://standards.nctm.org/document/eexamples/chap5/5.1/

And here is the above game without all of the instructions:
http://standards.nctm.org/document/eexamples/chap5/5.1/#applet

Virtual fraction bars. They can be used to teach or reinforce fraction concepts such as equivalent fractions, or addition and subtraction of fractions.