The problem with weighted keyboards is that unless the pivot point is a little back from the back end of the keys, the action feels uneven and some of the notes played with your longer fingers will jump out at you. A keyboard with a properly weighted action and nice long leverage is expensive and a beast to carry around.
Because of this, I just use M-Audio's very lightly weighted keyboards. I have two of them. One for my studio and one for live playing. Keep in mind that in both cases, piano is just one of the things I do. I also do plenty of strings, synth leads, pads and orchestral parts. For these I also need the pitch and modulation wheels. It also has to be wheels, not a joystick. Most orchestral voices have their volumes controlled by the modulation wheel which works well because it has more precision than 127 values, and is not spring loaded.
Anyway, here are my two M-Audio keyboards:
I have this one in my studio:
http://www.m-audio.com/products/en_us/K...n88es.html
It also comes in black now:
http://www.m-audio.com/products/en_us/K...88New.html
I use this one live:
http://www.m-audio.com/products/en_ca/P...ono88.html
What I like about it is that it's as small and light as an 88 note keyboard can be and the USB audio interface is built in. To use as a Midi keyboard / USB audio interface, there is a button and key sequence that turns off local control and silences the built in voices. Another cool thing is that you can also mix in another stereo audio source which means that you don't need a mixer if you use a second keyboard (mine is a Roland VR-09). You can also quickly go to the internal sounds if your PC crashes which can save the day if you are in a group setting.
As far as the action goes, it is ever so slightly heavier than an organ keyboard, but nothing to brag about. Once you set up a proper Pianoteq curve and play with it for a while, it's fine though. Light but solid.
Both of these keyboards are really inexpensive. The midi only one is about $200, and the one with the built in audio interface is about the same price as if you bought that keyboard plus a separate interface. Not for everybody here I know, but I really like them.