Supporting Advancement is a website run by Bryan Dowling of the University of Michigan.  It is a treasure trove of helpful hints and sample materials submitted by programs from around the world.

Mal Warwick is a direct marketing guru.  His articles, newsletters and books provide a wealth of information for the annual giving professional.  He also provides a 'confidence calculator' to quickly determine if your sample size is large enough to provide meaningful results when testing new strategies.

Don't Tell the Donor.org is an interesting blog focusing on news and opinions from the world of nonprofit fundraising.  Written by an anonymous fundraiser, it always provides a humorous and critical look at our industry.

Charity Channel provides a community of nonprofit professionals a place to share ideas and hold discussions about the world of philanthropy.  The site provides book reviews, articles and other resources, some of which are free while others require an additional fee for use.

The Center on Philanthropy at Indiana University provides nonprofits with a variety of resources including cutting-edge research and educational programming.  Also home of The Fund Raising School.

Portico is a collection of websites for advancement professionals to locate public information on donors, prospects and organizations.  Portico is hosted by the University of Virgina.  While not updated regularly, most links are currently in working order.

TED: Ideas Worth Spreading started out as a conference for 'the world's greatest thinkers and doers' and was a very exclusive annual event.  Now, TED presentations are available for online viewing.  Treat yourself to a few TED presentations and you'll be both inspired and addicted.

Presentation Zen is a blog about professional presentation design that includes helpful commentary on designing your next PowerPoint presentation.  PZ also includes examples and critiques of interesting presentations.

Oldies but goodies:

Council for Advancement and Support of Education (CASE)
Chronicle of Philanthropy
Guidestar