Is there a quick way with macvim/NERDtree plugin to find a file?

You should also check out the builtin command :find.

First, you need to define what directories to search. If you wish to recursively add the subdirectories of /path/to/project to your search path, use:

:set path=/path/to/project/**

You can then open e.g. /path/to/project/then/some/random/subdirectory/filename.ext by issuing:

:find filename.ext

To open your search result in a new tab or split-screen, try :tabfind or :sfind instead.

Edit

I just noticed that you're looking for fuzzy matching of files, in which case I don't believe :find is up to the task. You may be interested in the :Find function defined in this vimtip though.

Since we are all listing alternatives here, Command-T is another fuzzyfinder-esque plugin that attempts to mimic textmate's find function.

Docs can be found here.