Thank you very much to everyone who responded - you have resolved my issue.
Here's what I was doing wrong:
I would go into finder, click on "Applications," and find "Sketchup 7." Then I would open up that folder, find the Sketchup icon, and right click to review "Show package contents." I would then put my items in the plugins directory. And POOF! Nothing would happen.
As several of you suggested, I should have instead browsed to Users-blahblah-library-application support, ect.
Putting the plugins here fixed the problem! Again, thank you to all who helped me resolve this issue.