jQuery 1.4.2 is out- not officially on their website, but you can be sneaky and get it here:

http://code.jquery.com/jquery-1.4.2.js

http://code.jquery.com/jquery-1.4.2.min.js (not really "minified" as much as "closure compiled"... can we get a verb for that?) The changelog isn't up yet, but that's generally the last thing to go (and hey, we snuck in the back door to grab the update anyway, right?) I imagine it'll eventually find it's way to their API page for 1.4.2.  I ran a quick diff; here's some changes that I found notable from jQuery 1.4.1 to 1.4.2:

• Optimizations for the body selector
• A few changes to how arrays of elements selected are built, I'll go with my gut and say that they're optimizations too
• Trimming whitespace from JSON data responses, for good ol' IE
• A more few various bugfixy-looking things, mostly targeting IE
• It looks like there was a lot done to the event-adding code; I think mostly internal changes. Probably more optimizations? I'll leave it to Resig or someone to explain whenever the changelog comes out. A few (generally pretty deep) methods had some parameters changed, or were renamed (things like "jQuery.event.special.submit.remove" becoming "jQuery.event.special.submit.teardown")
• A smattering of changes within "live" and "die" mostly centering around the usage of namespaces
• Blackberry browser bugfix concerning converting NodeLists to arrays
• jQuery.getText changed to jQuery.text
• Changes to caching fragments to help out WebKit and IE 6

I haven't really dug too deeply in the jQuery core before, so I'm not totally qualified to give a whole lot more detail than that. I used SourceGear Diffmerge between 1.4.1 and 1.4.2 to find out what I found out.

Also, in related (and perhaps more official news),  the jQuery UI team released jQuery UI 1.8rc2 - which includes bugfixes in the already pretty stable 1.8rc1 (changelog). You can grab it:

http://jquery-ui.googlecode.com/files/jquery-ui-1.8rc2.zip (development bundle)

As of right now, I'm testing it in our application at MeM. Let's see how things go!