I use an Enermax 'noisetaker PSU' which has 2 very quiet fans in it.
The thing with fanless PSU's is that you still need a way to remove hot air from the case, which means more case fans so it's all swings and roundabouts IMHO.
I'd also recommend a single 80mm/120mm fan at front and back of case to bring in fresh air/take out warm air. Attach a couple of Zalman fanmates on each of these, and turn the speed up to about halfway.
This will mean less hot air running up through your PSU, which will prevent it from ramping up speeds if it's automatic.
On the CPU, the big circular Zalman copper heatsinks with a large fan in the centre are very quiet (they also come with a fanmate) and Arctic cooling do some good quiet CPU fans.
Your weakest link at this point will certainly be your graphics card, they are usually very noisy, especially on high end models. Choose one with no fan or get a quiet cooler for it (again see Zalman or Arctic Cooling for options)
If your Motherboard has a fan on the Northbridge then that will also make a racket, consider replacing it with a passive cooler, Zalman (again!!) do a decent one.
I've also tried some of the PC Case acoustic foam but it doesn't really help unless your case is thin and flimsy in the first place.
Shop around because prices do vary from one retailer to the next. Specialists such as quiet PC and the like seem to charge a premium for quiet cooling products. You may find the same stuff cheaper at a local shop or computer fair.
Checkout
http://www.silentpcreview.com/ for reviews.
If things get very bad consider lining your computer case with drywall and rockwool
Hope this helps! (and no I don't work for Zalman!)
