there isn't anything on mac like add/remove programs from windows where it lists all you installed programs and gives you an uninstall button..
it works kinda different on mac, you have an application and it just that one thing, you have an option to show contents which sort of opens it as a folder and in there is all the files that build up the app.
So most simple apps are just that and all you do to install it is drag it to the applications folder (or any folder for that matter) and it's done.
Some of the more complex programs (i.e. ms office for mac) have an install program which copies that one file mentioned above aswell as various files to hd/library and hd/users/username/library.
The simple style app is easily deleted by just trashing it. the more complex type you have to open the install app and there is normally and uninstall option in there.
Now something like sql, depending on exactly what you installed is like to be the complex kind as it has to open ports, start at login etc etc what ever it needs to do which makes me think that by just trashing you may slightly wrecked that (but i'm not positive)
what exactly have you installed to get php/apache/mysql.. are you using the built in function in tiger?
p.s once this is sorted i would recommend getting MAMP again, i've been using it a little while now and its stupidly simple, no config, it's stable and you just run it when you want by launching the app.