Screenshots: before and after.
Firefox 4 and Internet Explorer 9 already support improved font smoothing offered by the DirectWrite API in Windows 7 and Vista. Google Chrome (WebKit) has yet to support DirectWrite, which may be the deal breaker for you when choosing to use either Google Chrome or Firefox if you are primarily a Windows user.
I recently discovered while messing with the CSS3 text-shadow property in Google Chrome that it somehow improves font smoothing in Google Chrome (but surprisingly not the WebKit-based Safari too). To use the better font smoothing on your website, just use text-shadow: rgba(0, 0, 0, .01) 0 0 1px in your CSS on whatever you want to have better font smoothing. I have also created a Google Chrome extension called “Enhanced Windows Font Smoothing“, which applies this CSS hack to every website and to all text. Please note that smaller text may look a little unsightly, though it will still be completely readable. For a good example website try the extension on, see how the text logo on the Ubuntu Font Family website looks before and after installation of the Google Chrome extension. Please note that this CSS hack may cause adverse side-effects on Mac OS X, so I suggest that you try to target Windows UAs only.