I've put a new version up that has the selection to LRF file support. Since several folks seem to really want it, I've put it on my site but not yet in the update feed, so you'll need to install it manually.
I've not tested it yet in Firefox 3.0, so this is for folks who just can't wait.
Version 0.3.6
Sometime tonight I'll fix a few more bugs and do some more testing and then I'll put 0.3.7 out and add it to the update feed.
To use the new feature, select some stuff, bring up the context menu and select "Selection To LRF". There's also a Hide Element menu item. If there's some stuff in the middle of the selection you don't want to see in your final document, right click on it and select Hide Element. This just sets the visible attribute to false, if you refresh your page everything resets. Also this doesn't work when building a LRF file from the entire page using the normal process.