Bike: fenders are a must
Legs: tights or leg warmers are usually sufficient. I have rain pants, but even though they are breathable, they get hot too easily so I tend to use them more when I need a wind layer for sub freezing temps than for rain.
torso + arms: I go back and forth on this. Currently have an older ultra-lightweight endura jacket (that could stand to be more breathable) and one of their bulkier models that vents better but stands up pretty well to moderate-heavy rain.
head: sealskinz skull cap (reasonably breathable and rain resistant) or just a headsweat (warmer temps) and head is getting wet. I have a helmet-mounted light so can't easily put on a rain cover.
key are hands & feet. If they are dry, I'm happy. Hands: best is a pair of sealskinz wind & rain resitant gloves, I have glove liners if I need more warmth and keep an extra pair of gloves (cheap neoprene) at work just in case. Pear Izumi amphibs are great but generally too warm for rain conditions.
Feet: this is the tricky part. Lake cycling boots are reasonably water-resistant but I really need to make sure tights or leg warmers are dressed over the boot tops to keep water from running down into the shoe. I've also tried sealskinz waterproof socks (their ad shoes someone's foot in an aquarium tank) and regular MTB shoeswith some success - again you need to do something to keep water from running down legs into socks as whatever gets in will stay in. rainproof shoe covers are another option - the lightweight ones (endura) are water resisatant but not waterproof; the more effective ones (I have some PI model) run warm for me. I haven't tried Sealskinz with sandals - that might be the best solution.
Other: cycling glasses with clear or light amber lenses to keep rain out of eyes. Lots & lots of lights - helmet light, Dinotte 200 on handlebars, either 3 PBSF (bike 1) or a big cateye + Dinotte taillight (bike 2) with some steady, some flash.