An alternative to the interactive git rebase. (I like this method better.)

git-squash.sh

# Reset the current branch to the commit just before the last X:
# X is here the number of commits to squash together
git reset --hard HEAD~X

# HEAD@{1} is where the branch was just before the previous command.
# This command sets the state of the index to be as it would just
# after a merge from that commit:
git merge --squash HEAD@{1}

# Commit those squashed changes.  The commit message will be helpfully
# prepopulated with the commit messages of all the squashed commits:
git commit
# or...
git commit -m "<...>"

# If you want to push to remote
git push --force