Further Your Career as a Proofreader or Editor
Like all Catch-22 situations, to become an editor, you need editing experience. And to my mind, a great place to start is with Project Gutenberg. Project Gutenberg is the original site started to digitize books in the public domain to make them freely available world-wide.
However, as always, take care if you want to offer any of these books as a free download from your own site. What may be in the public domain in one country may not be public domain in another.
The site is always looking for volunteers to help with the proofreading and editing of each new book added. If you can commit to proofreading at least one page a day, you may volunteer as a proofreader and gradually work your way through to more advanced layers of editing.
There's strong support on the forums and even if you don't need the extra credits, it's a brilliant way to help out a great cause.
Further Your Career as an Audio-book Reader
Like Project Gutenberg is LibriVox, providing free audio recordings of books in the public domain. Their aim is to cover each and every book in the public domain.
All you need to volunteer is a computer, free recording software and a microphone if you have one. There are no auditions or speaking tests. Every possible question you might have before beginning is answered in the FAQ sections of the forums.
Other opportunities can also be found advertised in different sections of the forums. You may be working as an unpaid volunteer, but you will be gaining valuable experience and making cyberfriends interested in the same topics.
Further Your Career as a Library Cataloguer
Hoping to develop a library with one web page for every book, The Open Library already has over one million titles listed. Not all are free e-books, however, though you can also use it as a link to borrow many twentieth century e-book titles.
You can add books, edit pages, report any inaccuracies, add book descriptions. Again, it has a comprehensive list of Frequently Asked Questions.
And if they're not already added, why not add your own books and a list of website addresses where they can be obtained?
That way, you can further your career as an author too.