The biggest one is PHPMyAdmin. LAMP's a pervasive thing. (Not that I like LAMP, mind you, but it's important to be aware of why Pg hasn't made large dents in the MySQL market share over the past decade.)
phppgadmin? I've used both (using phppgadmin right now), and they're similar enough. It's not as nice as phpmyadmin, but that shouldn't be a determining factor over whether to use mysql over postgresql.
Thanks for the feedback. That explains a lot then. I always preferred to use the command line, so that I could either make scripts, or at least screen shots, of changes made. Thus, my utter lack of concern about the admin GUIs. PostgreSQL has a kick-ass command line tool, with online help, GNU readline (including auto-complete), annd good output formatting options. Contrast with Oracle's sql*plus tool (yee-UCK!). I seem to remember mysql having at least readline, but not sure about the rest (probably comparable, but who knows).