On his blog (and in a comment on my 120 DPI post) Omar points out a super-secret registry tweak make IE do extra scaling in high DPI mode. IE already adjusts for well-written web pages, but if you're using high DPI and still feeling cramped on some sites, you might want to give it a shot.
I don't like it because it has a tendency to distort graphics, and it makes some fonts too big for my displays, but it's good to know about. I mentioned an alternative in my own comments a few weeks ago, but I suspect not many people saw it. For the occasional web sites that hard code small font sizes, here's a very simple “per-page zoom” workaround:
1) Create a local file (i.e. c:\web\zoom200.htm) that has the following script:
2) Add it to the right-click menu in IE, by adding a registry key:
Key: "HKCU\SOFTWARE\Microsoft\Internet Explorer\MenuExt\Zoom 200%"
Value (Default): "c:\web\zoom200.htm"
Adjust the zoom percentage and file locations as needed and then restart IE. Now when you right click on a page the menu should have a new option to “Zoom 200%”. Clicking on that will zoom the entire page, including graphics and (most) controls. A 125% or 150% zoom is probably more reasonable for normal reading; I've created several zoom levels in this way. Unfortunately zoom has a few issues with font kerning/spacing, selection, controls, and an overall lack of polish, which is why you don’t see this exposed directly in the browser yet.