Private Browsing 1.0 Pre-Release 1
Private Browsing by PortableApps.com is an add-on that works with Mozilla Firefox, Portable Edition. It allows you to launch Firefox with an independent profile from your normal Firefox Portable profile. This profile has persistent cookies, history, download history and other privacy features off. Flashblock is also included to block Flash Cookies and other nasties. A custom theme and branding is included so you can easily distringuish your private profile from your normal one. It works similarly to the upcoming private browsing features in Firefox 3.1 as well as similar features in Safari and Google Chrome.
Download: Private Browsing 1.0 Pre-Release 1