My favorite 'mind training' work is Shantideva's Bodhisattvacaryāvatāra. Technically this is not a lojong text but it always struck me that in purpose it most certainly is. I also remember reading somewhere that HHDL said something to that effect as well.

As for lojong, Geshe Sonam Richen's Eight Verses for Training the Mind is a great little book (I really like his translations).

B. Alan Wallace's A Passage from Solitude is an exposition on another core lojong text, Geshe Chekawa's Seven Points for Training the Mind.