Mozilla added some Geolocation ability into the new Firefox 3.5 – I rather quickly whipped up this bookmarklet: ⊕

Click it if you want to see where Firefox thinks you are, drag it to your firefox bookmarks bar for quick access if you want.

Edit: Please note, while Firefox says that you’ll be sharing your location with whatever site you’re on whenever you click this bookmarklet, it’s not true (at least in my case).

Edit 2: This also works with the iPhone, with better results as Webkit uses the phone’s location frameworks, instead of Firefox’s (I presume) IP based location.