Can't save any more selections!!

I have been working on a piece of work in photoshop which requires me to make numerous selections and save them. So far I have made 20, and it will not let me save any more unless I overwrite old ones. Is their a way of increasing the amount of selections that can be made, or a way of deleting the uneeded ones.

Oh and if anyone can point me in the direction of any tutorials for rendering camera's or chrome surfaces then it would be much appreciated.

Thanks

Photoshop 7 can have up to 24channels. Photoshop CS increases this to 56, I think...

Look in your channels palette, you'll be able to move the ones you don't need to the trash.
Another solution is to store them in Layer masks... (create a set for selections, and create new layers, then hit the layer mask icon, while you have a selection active... It might take some room. Maybe using another document would be an idea.

Converting simple selections to path might be an area to explore, too...