What is the modern day equivalent of Firesheep?

Solution 1:

Cookie Cadger, being developed by a colleague of mine. Terrifying Java app that steals cookies from a large number of apps:

http://igniteshow.com/videos/cookie-monster-unnoticed-threat-open-wi-fi

Edit: Available now at https://www.cookiecadger.com/

Solution 2:

To my understanding, all that Firesheep did was sniff out unsecured packets and pulled the information from there. Unfortunately there isn't a replacement extension (to my knowledge), but there are other options.

Wireshark does exactly this. I'm not as well versed in it's proper usage as I'd like to be, but there are many guides out there that can help you utilize it's functionality.

Solution 3:

There is also DroidSheep for Android (requires root). The source is also available.