While making a copy of all your pictures is a good idea, we call it making a "Back Up", it is NOT a good idea to keep that copy on the same HD as the originals.
When disaster strikes, it will most likely be in the form of a hard drive failure. At that point, your copies are as good as a two legged milking stool. (among other analogies)
Copy your pictures to a CD or DVD and store them in another location. Use an external HD if you don't want to mess with CD/DVD's but be aware that ALL hard drives WILL fail eventually.
I think you are confusing Memory with Hard Drive space. Copying your pictures will take up HD space but will have NO effect on the memory (RAM) (discounting virtual memory and the problems with a full drive)
I don't know of any application that will do what you ask but you can Get Info on folder and files to see how large they are. It does not take long to fill a 30Gb drive.
P
In an earlier post I described how my iPhoto would crash while trying to browse the library and there was no clear explanation or solution. Thinking that I may have to save the photos externally for more drastic measures I created a new folder and copied and pasted the photos from the library into it. I then deleted all the pictures in the library, closed the program, rebooted, and reopened the program. It stayed open. I then reversed the procedure, put the pictures back into iPhoto, closed and reopened the program, and lo and behold it stayed open when I browsed. I don't have a clue as to why.
I've never been in the habit of saving copies of my pictures in any location other than iPhoto but I hope to get into the habit now in case disaster strikes. But saving also means using more memory and I know with my 30 GB iBook, I'm running on low (I hope to buy a new one soon) ((it would be nice for Jobs to offer price cuts for those purchasing a new computer, iPhone, and/or iPod together)).
I have a question though, is there a place in the OS (10.4) or a program that can be installed that will tell you where all your memory went for housekeeping purposes?

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