Definition of 527's, according to Joseph E. Sandler and Neil P. Reiff, who are partners in Sandler, Reiff & Young, a Washington, D.C., firm that specializes in election law. Authors of the book "Bipartisan Campaign Reform Act of 2002: Law and Explanation," they counsel Democratic candidates, more than 35 state party committees, PACs, nonprofit groups, donors, political consultants and other entities:

"Section 527 is actually the section of the Internal Revenue code that allows all partisan political organizations to take contributions without paying taxes on them, to the extent the money is used on political purposes. Technically, every political committee at any level -- from the Republican National Committee (RNC) or Kerry for President or Jones for dogcatcher -- is a section 527 organization.

In the current vernacular, it is used to refer to groups that are political organizations for federal tax purposes but not under campaign finance laws, particularly federal campaign finance laws. And if such an organization is not a political committee for purposes of federal campaign finance laws, there is basically no legal limitation on the source or amount of contributions to the organization."

Source: Sandler, Joseph E., and Neil P. Reiff. "Consultants' Corner." Campaigns & Elections, August 2004.

"Total amount raised since August 2000 by 471 committees registered as 527 groups: $654,691,322"
Source: Center for Public Integrity

As far as what will happen with 527 groups in the future, your guess is as good as ours.