I've installed a few plugins lately and activated them and set their settings, but when I go to the appearence page they do not show up as being available to place on a sidebar. Why is this?

Not every plugin is or provides widgets

Flynn, Why does the plugin "ebaystore" not work even when I put it on a page. The instructions are:
"Usage
Create a new page and insert the following code : [ebaystore:id] . Just replace “id” with your ebay store id.

Example : [ebaystore:123456] "

I do the above but only the number "1" shows up on my page. What am I doing wrong?

Try with the "Default" theme to see if this is caused by Atahualpa

No. It doesn't work with the default theme either.
I guess I need to contact the plugin author.
Thanks for your help.