Here’s my Dell Mini 9 running Mac OS X Snow Leopard 10.6.1.
I followed the instructions on MyDellMini.com to do the upgrade from Leopard 10.5.7. The internal drive has been upgraded to a RunCore 64GB SSD so the easiest way to upgrade is to remove it, connect it to another Mac via USB, then do all the installations before refitting it in the Mini.
Don’t forget to DISABLE the Legacy USB support in the BIOS to prevent the computer locking up in sleep mode.