Two of Us: Inside the Lennon/McCartney Connection
Quite possibly the best analysis of the Lennon/McCartney partnership that I have ever read.
Phil Spector and Let It Be
My favorite Beatles biographer (his whole blog is worth reading) on why having Phil Spector produce Let It Be wasn't such a bad idea.
John Lennon and feminism, or: not a simple story
Why John Lennon's conversion to feminism is not entirely convincing. selenak's other Beatles posts are worth reading, too.
It's Not Just About the Word
On a incident at SlutWalk last year involving a controversially-titled Lennon/Ono single, and whether people who aren't black should ever use certain words.
Some Beatles-related tumblrs that I enjoy that are still updated regularly:
Oh No They Didn't Beatles
Lots of fantastic pictures, short excerpts from books, and of course, music (such as this gorgeous cover of "Julia")
Pizza and Fairy Tales
One commenter referred to this as a "John and Paul research blog" :). There's stuff about George and Ringo, too. Lots of great quotes, pictures, audio, videos, and music. Also, great tags, things like: surreal it like dylan, projecting issues onto George, unfortunately for Paul, George can you know TALK, ringo sure loves octopuses, bizarre family dynamic, and my personal favorite, HOW IS THE REAL LIFE.
I'll Never Lose Affection
Good pictures, quotes, and videos. Like this lovely quote from Yoko Ono: "Once you know somebody, you can never unknow that person. And knowing is loving. So you can never get out of love. There might be misunderstandings and separating for other reasons, but love is always there. Staying together is just one form of love. Maybe that’s a strong love and expression of love. But love is a soul thing. It always stays there."
Fuck Yeah Yoko Ono
All things Yoko Ono. Pictures (both of her and of her artwork), quotes, music, videos. I never quite know what to make of Yoko's artwork, but I think her "Play It By Trust" chess set interests me the most. Cara, who runs this tumblr, also runs a John and Yoko tumblr that I enjoy.
Also, while it's obviously not a tumblr that is currently being updated, May Pang's memoir ,<i>Loving John</i>, about her experiences being in a relationship with John Lennon is available in its entirety to read on tumblr.