What can an unemployed job seeker do to keep their skills sharp?

What can an unemployed job seeker do to keep their skills sharp and relevant while they are searching for a new job?
There are several ways to keep your skills sharp:

1) Volunteer your services to non-profits and small businesses.  You need to make sure you are offering your services in the area of your job skills/expertise.  Example:  You are a web-designer.  Offer to redo a small business website with the understanding that you can place your logo and designed-by contact information on the pages.

2) Continue your education.  Use those training and certification classes as networking opportunities as well as keeping your skills sharp.  Most likely the people in that class are being sent there by their company to gain this new skill and may be looking for additional resources.  Add these people to your LinkedIn.com network and ask them for their recommendations, endorsements and possibly add them to your reference lists.
3) Develop/create your own utility or product that uses the skill you want to advertise and promote.  This could be a tool that you offer free on the internet – OR – a presentation video on YouTube – OR – a training video on YouTube, facebook, linkedIn, etc.

The goal is to come up with ideas that both keep your skills sharp and helps get you that job.  Each of these solutions have an affect on your resume and cover letters.  You gain additional work experience, recommendations, and references for your resume and cover letters.  You can also refer potential employers to your internet product or YouTube training videos.