Helm for Emacs is a fantastic Quicksilver-like extension, but it gets quite wordy sometimes. Instead of C-u M-x helm-do-grep *nav to dir* *enter extensions* *enter query* to recursively grep, I defined the following in my init.el. Now hitting F1 will grep actual source across all my projects.
(defun project-search () (interactive) (helm-do-grep-1 '("/home/vaughn/src") '(4) nil '("*.clj" "*.cljs"))) (global-set-key (kbd "") 'project-search)