The FictionAlley forums comes first in my list of favourite sites. Though I tell myself, repeatedly, that I've overcome my Harry Potter obsession, I always drop in to visit the VENOM forum and get my daily intake of "Can't Stand Character/Ship/Situation X". It's a morbid amusement, enlightening on the occassion, and never boring.

Skipping from that pinnacle of my preference to the sites that form preference's core:

• Blogger; LiveJournal(I roam through various journals and communities on LJ, and am inexorably drawn to HP meta despite the headaches that come with reading it, but my favourite place to lurk is The Pitfalls of Fanfiction, or fanficrants community.)
  
• The Phrontistery (lovely, lovely site for vocabulary exhumed from the most obscure and caliginous depths of the English language), Dictionary.com, Wikipedia, Urban Dictionary
  
• deviantART
  
• YouTube

Ooh, I love that site!

I generally keep at least four tabs open: one for the site in which I am currently browsing, one for Dictionary.com, one for whatever YouTube music video/ZreoMusic flash player I'm listening to, and one for miscellaneous activity: a glance at Wikipedia, a search engine needed on the spot, a website to peruse while another is loading.