Stephen over at Third Party Watch has a statement from Bob Barr's office on a possible run for President:

Former Congressman Barr has been receiving numerous calls for him to consider seeking the nomination of the Libertarian Party for the presidency of the United States. He understands this reflects in part the deep dissatisfaction prevalent among voters with the candidates of the two major parties. Congressman Barr is grateful for the many and continuing expressions of support for his potential candidacy. He has, however, made no decision in that regard.