The .git folder is only stored in the root directory of the repo, not all the sub-directories like subversion. You should be able to just delete that one folder, unless you are using Submodules...then they will have one too.
Unlike other source control systems like SVN or CVS, git stores all of its metadata in a single directory, rather than in every subdirectory of the project. So just delete .git from the root (or use a script like git-export) and you should be fine.
In case someone else stumbles onto this topic - here's a more "one size fits all" solution.
If you are using .git or .svn, you can use the --exclude-vcs option for tar. This will ignore many different files/folders required by different version control systems.
There should only be like 3 or 4 .git directories because git only has one .git folder for every project. You can rm -rf yourpath each of the above by hand.
If you feel like removing them all in one command and living dangerously:
//Retrieve all the files named ".git" and pump them into 'rm -rf'
//WARNING if you don't understand why/how this command works, DO NOT run it!
( find . -type d -name ".git" \
&& find . -name ".gitignore" \
&& find . -name ".gitmodules" ) | xargs rm -rf
//WARNING, if you accidentally pipe a `.` or `/` or other wildcard
//into xargs rm -rf, then the next question you will have is: "why is
//the bash ls command not found? Requiring an OS reinstall.
This command (and it is just one command) will recursively remove .git directories (and files) that are in a directory without deleting the top-level git repo, which is handy if you want to commit all of your files without managing any submodules.
find 2>/dev/null | egrep /\.git$ | xargs rm -rf
This command will do the same thing, but will also delete the .git folder from the top-level directory.