Google has just released three Firefox extensions. One is the Firefox version of their Internet Explorer toolbar, which still has some bugs in it (the checkboxes all look screwed up here), but I'm sure they'll be fixed before long. They also have an extension for sending text messages to your mobile phone, and an extension that adds the nifty Google Suggest feature to Firefox's built-in search bar.

Strong backing from large companies like Google is what will help sell Firefox to the masses. Most people don't care about standards support (although it's certainly the most important aspect of a web browser), but get well-known companies like Google to make cool and useful tools for it, and it'll spark a lot of people's interest.