I've mentioned vimgrep in a previous post, but I neglected to mention a few useful flags that can be used in conjunction with it.
If you apply the 'g' flag to your vimgrep, it will return all matches instead of just one match per line.
:vimgrep /foo/g **/*
If you apply the 'j' flag, Vim will not automatically jump to the first match.
:vimgrep /foo/j **/*
Thanks to Chanel for pointing these out.