Any simple power supply designs for a 24VAC transforrmer?
24VAC is an inconveniently high voltage for many applications, with high line voltage and lightly loaded (the transformer regulation comes into okay) its quite possible to get 45V or more at the filter output (input to the regulator). Not many inexpensive switching of linear series regulators (definitely not LM78xx) are rated to safely operate with that high an inout voltage. 

But if you do a parametric search for such regulators, they can be found, the details really depend on what output voltage and current you want. 

You would generally use a bridge rectifier and an electrolytic filter capacitor between the transformer and regulator. It's easy to calculate the capacitor size and voltage rating from requirements. 

For a switching regulator, something like an LT1767 would work, but there may be more appropriate parts for your requirements. 

BTW if your 24VAC transformer happens to be center-tapped, the rectifier can use just two diodes and you get a nicer voltage to work with. If you use a bridge rectifier you can get both positive and negative voltages from a single transformer. Very nice for analog projects.