Interestingly, there has been lots of talk on here about how the DS is outselling everything, the 360 is doing well and the PSP is failing Sony. Whilst i'd probably agree, i found it interesting when looking at EBay that the 5 most popular searches are:
1.psp
2.ipod
3.xbox 360
4.ipod nano
5.nintendo ds
1.psp
2.ipod
3.xbox 360
4.ipod nano
5.nintendo ds