http://sparkle.andymatuschak.org/
I'm not aware if there's anything similar for Windows.
I'm not aware if there's anything similar for Windows.
I like that Sparkle's open source, and it's being used by many open source apps on Mac already. Getting the auto-update software to actually be secure is not trivial either (a recent attack was discovered on Acrobat's updater for example).
I am not aware of a win or a Linux (I mostly work on Linux) solution either
I'm trying to say this without sounding snarky, but why the heck would you need this on an operating system that already gives you apt-get, pacman, yum, portmaster, or what have you?
As for Windows, apparently there's a WinSparkle now: http://winsparkle.org/
Also the WiX people have been working on something along these lines, but I don't know how mature that project is or if it's even still a project any more.
EDIT: Looks like Google's made a separate open-source project of its update framework, Omaha, which is apparently how Chrome gets its updates. So I guess you can get Chrome-style auto updates in your own applications now. Don't know if Google's nifty binary diff compression algorithm is included.