The visual block mode of Vim is fantastic when you want to insert, append or delete from a certain column across many lines. The VimCasts video on Visual Block Mode is the best resource I have found to learn about this mode.
Ctrl+v: Enter visual block mode. Use jklh to move around and visually create the block.
To insert text in front of the block: Press I, then the text you want and press Esc.
To append text at the end of the block: Press A, then the text you want and press Esc.
To replace every character in the block: Press r and then the character you want to overwrite with.
To delete the block: Press d.
Tried with: Vim 7.4 and Ubuntu 14.04