Netbeans has subversion integration built into it, and function as a real-time diff from your working copy. It sounds like that would solve the problem the best. I don't use it myself anymore, and I don't know how it handles large files, but it's available on every platform, free, and will do what you asked. You do need to have a subversion repository, of course, though.
wiredog writes: At least 22 people have been killed and 21 more injured by a gunman (who is one of those killed) at Virginia Tech. This is a more people than were killed in the shootings at Columbine High School in 1999. A statement from the University President here. Coverage from the BBC, and The Washington Post.
Auke Slotegraaf writes: "Earlier in February, a nova erupted in Scorpius, and then flared up to naked-eye brightness. It is still (Feb 22) visible, and can be seen in the morning sky before sunrise. Then on the 19th, a second nova erupted, just 3 degrees away from the first! It is currently visible in binoculars. It is still unclear how bright the second one may become, but chances are we will have TWO naked-eye novae a cosmic hair's breadth apart! A finder chart of the two novae is at http://www.psychohistorian.org/astronomy/news/200
prostoalex writes: "Google Apps for Your Domain is going premium as custom 10 gig Gmail box, Google Calendar, GTalk instant messenger, Writely, Google Pages, Google Custom home page iGoogle and Google SpreadSheets for $50 a year per employee. CBS Marketwatch is calling it the "boldest move yet to challenge Microsoft Corp.'s flagship Office brand of business computer programs." The New York Times also provides some details on competitive pricing: "By comparison, businesses pay on average about $225 a person annually for Office and Exchange, the Microsoft server software typically used for corporate e-mail systems, in addition to the costs of in-house management, customer support and hardware, according to the market research firm Gartner.""
shoemortgage writes: "The Association for Computing Machinery, has named Frances E. Allen the recipient of the 2006 A.M. Turing Award for contributions that fundamentally improved the performance of computer programs in solving problems, and accelerated the use of high performance computing. This award marks the first time that a woman has received this honour."