Chuck, it really depends on how much you want to spend. a good, cheap setup might be the ECS K7S5A+256mb pc2100+AXP 1600+GC68. that will run you about $180-185 with shipping. case really depends on your taste, i prefer the cheap cases, the enlights are nice if a bit ugly. some of the
newer enlight
caseslook pretty classy though and as another plus, enlight PSU's are quiet. if you can spend a bit more i'd reccomend a good KT333 board like the MSI KT3 ultra+256mb-512mb of pc2700(samsung is good but i like kingmax cuz it's cheap). either way you go, i'd get most everything from newegg and SVC, both are great retailers with great prices and service.
hope this helps
-nate
edit: seeing as you are on a p133 right now, would it be safe to assume that you don't do anything too system intensive? if so, you could go with the ASUS A7N266-VM for a mobo.