One of the best sites for job seekers is the Academic Jobs Wiki. Not only does it have postings, but people also update whether they've gotten past the first round, second round, phone or physical interviews, and other status changes including searches being shut down by provosts, etc.. This lets you know whether to keep hoping or to give up.
There are academic job wikis for other fields, I've only posted the physics one above.
Update 2019.7: please note that in the four years since posting this, I’ve heard several reports of people gaming the wiki jobs system: reporting a position closed when it isn’t, reporting a different direction to the search to throw off competitors, etc. As with all crowdsourced systems, use with some caution and only as a supplement to other sources of information.