A small plug for http://www.epowermac.com.au/shop/pc/home.asp who I found by following the link from Rick's recent post (which I could not refind to put this in!).
I have just purchased 4Gb RAM for my newiMac 24" (so I will have 2 x 1 Gb genuine Mac RAM for sale soon), 512MB RAm for my old Titanium laptop, and a battery for it. Very please with the price. Will post again when it has all arrived and I have installed it.