map <leader>d :execute 'NERDTreeToggle ' . getcwd()<CR>
Awww, isn't that cute? BUT ITS WRONG!!!1
It all comes from this blog post. OMFG Jamis Buck, I will find you, and I will fuck you. Then I'm gonna shove my entire $12 keyboard into your anus and turn it sideways before I squash you into a fetal ball and use copious amounts of superglue to bind your hands to your ass, and your scrotum to your tonsils. Then I'll bowl you down a hill into a set of garbage cans and put the video on youtube.
:NERDTreeTogglecommand defaults to the current working directory anyway. So, if you have the above line in your vimrc, delete it immediately and replace it with this:
nnoremap <leader>d :NERDTreeToggle<cr>