depends on you yourself.
how much you're willing to spend. how heavy are you willing to carry. what size you're looking at.
important factors to consider : price VS weight VS size VS performance
im using a lenovo y410 series laptop.
my laptop specs are
intel core2 duo(centrino based) t5850 @ 2.16ghz
3gb ram
win vista home premium
dvdrw
nvidia 8400GS(mobile ed) 128mb if i remembered right
bluetooth
card reader
14.1" widescreen
320gb hdd
2.4kg with batt
bought it during june pc show for $1.6k with extended warranty.
reason i bought was 2 things : Photoshop and games. games ran smoothly at medium and low settings. photoshop is nice and smooth too, occasionally i do video encoding too. did i mention there's a firewire port
this laptop model has different specs, another y410 model uses the Intel's GMAX3100 graphics.
another important point to note, more ram better. but we're using vista now, hard to get a win xp based laptop today. vista eats up ram, so does video editing and photoshop, so 3gb is good enough for me at least.
a GOOD BAG is important too, especially if you plan to bring it along with you. i carried my laptop+tripod+ camera bag(2 camera bodies with lens attached, 1 spare lens and flash) and ran like mad to take shots during NDP( dont ask why) after a while, you'll get used to the weight.
an important factor to factor in also is brand. choose wisely. ask more . do your homework too. comparing this laptop im using with my desktop, they're equally powerful
( usng an AMD AM2 4000+(2ghz o/c to 2.4ghz) with 2gb ram, nvidia 7300LE 128mb, dvd rw) , but of course, my laptop is wide screen
there are UMPCs though that are capable of using photoshop, but performance wise, lets not talk about it. and dont forget, UMPCs have smaller screens.. painful for the eyes in the long run...