ADDED: Here's a New Republic article from a couple months ago that's very positive about Al Gore running in '08:
...Gore is the only anti-Hillary candidate who can credibly attack her on both fronts. His early, vocal, and unwavering opposition to the war in Iraq has made him a hero to many Democrats. The Hollywood liberals over at Huffington Post as well as the university-town activists at Daily Kos and Moveon.org love Gore. If he ran, he would instantly become the favored candidate of the "netroots," the antiwar, anti-Bush crowd that championed Howard Dean and that will be a significant source of money and buzz in the run-up to 2008. The activists in the liberal blogosphere, more than any other opinion-making constituency in Democratic politics, revere Gore. They still wave the bloody flag of the 2000 recount. They still pump out bitter posts about how the mainstream media trashed Gore in 2000 yet gave Bush a free pass. They remember that Gore endorsed Dean in 2004 and they burst with pride at the fact that he chose Moveon.org as the forum for his most important speeches.
Of course, any antiwar candidate could criticize Hillary's vote for the war in Iraq. But the logic of the Gore candidacy is that, unlike other Democrats, he could attack Hillary as both out of step on the war and unelectable come November. If he runs for president he would be the only candidate in either party who instantly passes the post-9/11 threshold on national security issues. Hillary's credible case that as first lady she engaged in diplomacy and was treated abroad like a world leader would be dwarfed by Gore's eight-year record as vice president sitting on the National Security Council.
And Gore might be the only Democrat who can solve a vexing issue facing the party: How does a candidate establish a reputation for toughness on national security while simultaneously criticizing the war? Gore supported the Gulf War and, in most Clinton administration battles over the use of force, he took the more hawkish position. He is the party's only credible antiwar hawk.