Somehow I don't think any of these are what you're looking for (none are in retail circulation), but it might give you some ideas:
Cheap Thrift-Store Keyboards: I've been collecting cheap ($1-$4) keyboards/electronics from Goodwill for fun and future circuit bending; I visit a few times a week, and find some weird stuff. My favorites so far are the
Yamaha VSS-30 and
Casio SK60. In the "freaks" category, a
Kawasaki keyboard (whose pitch increases with the tempo), the
Play & Jam (which is a half-step below the note you think you're playing), and the
Stylophone (play a keyboard with a stylus? and no volume control? with an
awful buzzing sound?). None of these have polyphony greater than 4 or so, nor built-in MIDI support, so this probably isn't what you want. But damn, they're fun.
It's several years old now (so my opinion is probably outdated here), but my favorite consumer-level keyboard has been the
Yamaha PSR-520; it goes for $100-$200 on eBay lately. The sounds lack a bass-y punch, but overall are pretty good for MIDI compositions. Some old songs I recorded on it from '99:
synth-guitar rock,
laid-back,
piano jam.
More recently, Bolio's turned me onto the
Yamaha PSRD1-DJX keyboard, which I got for $100 (mint) on eBay. The presets are geared more toward techno/electronica stuff, but the bass is solid and the non-techno instruments are decent for this price range. Also, it has a pitch bend, which allows great expression and doesn't always come in the $100 range.
Since you don't like the pawn-shop idea, and I don't know much about current offerings, all I can suggest is:
1) Pitch bends are expressive, especially whenever you want to simulate a stringed instrument; try to get one on your 'board
2) Modulation wheels are nice too, but (imho) not as important as a pitch bend
3) Check for midi input and output ports; not all keyboards have this
4) If you don't plan to play live much, don't pay too much attention to the keyboard's built-in synth. It's good for generating ideas, but you'll probably find you can get great studio-quality sounds by using software synthesizers and soundfonts.
5) Weighted keys are problematic when recording live keyboard-drum takes; it's hard to hit the same key several times in a short period of time
6) If you can, test the keyboard's action before you buy it. Different brands/models react differently to your touch; some feel flimsy (e.g. Yamaha typically does for me over time), others more sturdy (e.g. Casios hold up better in this house)
7) Sustain pedals are also hugely important (and they're cheap). Most keyboards seem to have sustain ports these days, but you might want to check anyway.
Anyway, those are $0.02 from someone a little out of touch with reality.
