I got PostgreSQL from here.
Since I'm on 10.7 OS X, I'm having problems.
I want to uninstall the software I got from enterprisedb.
This question came from our site for professional and enthusiast programmers.
There is a one-click uninstaller that removes everything except the data director and user account. The default data directory is /Library/PostgreSQL/$VERSION/data, so rm -rf that directory (or wherever you instructed the installer to create it).
To remove your postgres user (assuming it is named 'postgres'), first list your users to verify that the user 'postgres' and group 'postgres' are what you expect: (just a safe check) before deleting anything.
Look for the "real name" field, to ensure that it matches the version of the db you are removing.
Then remove the user and groups:
Obviously, be careful when using sudo.
The uninstallation instructions are at the bottom of the installation guide linked from that download page.