Abandoning a package
If you are the author or maintainer of a package, and wish to step down, there are a few steps. To just orphan a package, you can use the maintainers page (at http://hackage.haskell.org/package/_yourpackage_/maintain) to edit the maintainers group to remove all maintainers including yourself.
If you think the package should no longer be used by anyone, you can deprecate the package, optionally providing a list of other packages which you think supersede it. You may wish to also orphan it in this case, to allow others to take it over or claim the namespace.
Finally, if you think that the package is still good and useful, but no longer have the time to maintain it, you can reach out via the usual community channels (the haskell-cafe mailinglist available via http://mail.haskell.org, reddit, etc.) to solicit volunteers to step in. Once you've found volunteers to step in, you should add them to the maintainers group to allow them upload rights.