I took iPhoto off the dock and now it's gone. Where did it go?

Removing it from the dock just removes a shortcut. Look in your Applications folder.

reinstall from the original source

Could be

1 - the restore disks that came with the computer

or

2 - the iLife DVD that you purchased

or

3 - the app store - log in under the Apple id used to purchase the software or to set up the computer - look under purchases - you might have to unhide or accept the Application first

LN

How was that obvious from what you wrote?

and again it is certainly obvious that the solution is

reinstall from the original source

Could be

1 - the restore disks that came with the computer

or

2 - the iLife DVD that you purchased

or

3 - the app store - log in under the Apple id used to purchase the software or to set up the computer - look under purchases - you might have to unhide or accept the Application first

and it is not at all ovvious that you did look in the Applications folder before posting and it certainly is obvious that you have not actually resolved the problem by reinstalling as suggested

LN

One of the problems with Internet fora like this is that we have no idea of the experience or knowledge of the other person in the dialogue. You could be a Professor of Computer Sceince. You could be 14 years old. You could even be a 14 year old Professor of Computer Science, though admittedly that's a long shot. I've seen posts on here from folks who think the app lives on the Dock and removing it from there deletes it from the Mac. I've seen posts from folks who don't know they have an Apps folder at all. These are not rare posts.