What makes sand on the beach and do we keep getting a little bit more all of the time?

The waves and wind make the sand.

as the waves crash onto the beaches, they crush rocks together, and in the ocean, rocks are rubbed together.

this creates little chuncs of rocks.
these chunks also rub together, creating smaller chunks, and so forth, creating sand.

in some oceans, where there is lots of coral, it is the coral that is also erroded into sand, that is why some beaches have white, or colored sand.

this crashing of the waves does deposit more sand on the beaches, but when the waves retreat back into the sea, they also take sand with them.

in some areas, there is more taking than giving,
these beaches are erroded,
but the sand from those beaches is taken and deposited somewhere else, where there is more giving than taking, so the beach grows.

hope this helps
-chris

Chris' answer is definitely worth a 5star rating, however the response forgot to point out that seashells are often a major contributor to the sand deposition on a beach. Essentially the answer is whatever is available (e.g. silicates, seashells, even volcanic lava which has solidified) will eventually be broken down/eroded to form the sand by the crashing of the waves.

A site with some interesting facts about sand can be found by clicking here.

I knew i would forget something,
thanks for being on top of things Mirannda.
Nice Link!
-Chris

Have you ever noticed that some beaches are hot underfoot and some aren't?

The difference is that rocks absorb heat. If the sand is made up of particles of rock, they'll get hot. If the sand is cool or only slightly warm, it's likely to have a very content from shells.