Ajahn Thanissaro's pronunciation guide from Wat Metta chant book.
(This one is my favorite guide for just getting started, as it's short and concise, covering the most basic and important rules.)
Ven. Ānandajoti's pronunciation guide:
this page shows some exceptions for the heavy weighting on the syllable preceding a double consonant
(oudated page which needs updating and possible removal of some items)