Get a power supply that is at least 400 Watts and that is a reliable brand name. If your PSU dies, it's all over... and it might take the rest of your components with it.
I have been using Fortron PSU's the last 2 years and they seem to be very very excellent... ranked best in stability over all in a few different hardware sites as well.
For ram you will want at least 512 MB of the fastest that your CPU/Motherboard can support. If your CPU has 400 MHZ FSB, then get DDR3200 (it runs at 400 mhz.) Match your CPU FSB to ram accordingly.... though beware of anything over 3200, as it generally runs hot and is primarily used for Over Clocking your Chipset/CPU.
That's all I am going to say... because the rest of the components are about personal preference.