Staffa and Lunga are both part of the Treshnish isles just off the West Coast of Mull. Staffa is a small volcanic island with awesome columns and some cracking caves (Fingals is the famous one). It has a small colony of Puffins on it. Most of the boat tours do a drop off/pick up on Staffa and you can walk about on the island and go into the cave a little bit.
Lunga is a bit further North and a much bigger island. It has one of the best sea bird colonies in the UK with a wide variety of birds there. If you want to see Puffins, this is the one you want (not Staffa). The colony is nearly 10 times the size of Staffa.
Most of the boat tours will go to Staffa (the Lunga ones will at least do a drive by of Staffa and head into Fingals cave (for me, this is plenty, but I do wildlife for a living!).
You can get to both islands from a variety of locations with Staffa Tours and Turus Mara. West Coast Tours offer it, but the boat part is Staffa Tours. Staffa Tours operate from Tobermory and Ffionphort in the North and South of Mull respectively. Turus Mara operates from Ulva ferry in the middle, near the islands themselves.
For any photographers out there with kit questions, you can easily take pretty much everything with a 70-200.
Photos Courtesy of Days in the wild