IBMs old servers, EMCs old storage. Wonder when they'll start reselling Cisco 3560's and Brocade 200E's?
That said, the 5100 was pretty popular with telcos in distributed offices. I saw a bunch of them in that role and as far as I know, they are still there. Most people buying them for general usage were pushed towards the 5300 from what I've been told so they could have the option for more FAST cache and file services down the road.