I'll toss in a plug for SBaGen.
SBaGen -- Binaural Beat Brain Wave Experimenter's Lab
It's easily the most obscure user interface of the bunch - no GUI, it's all DOS-based, but once you work through the user instructions, it's pretty powerful and it comes with a large number of samples to get you started.
What I like:
- polyphonic - I've had it running at least 5 voices simultaneously - much past that and I have a hard time hearing it
- able to produce "presets" by editing text files
- portable - I run it off a removable USB drive
- small - 2.8 MB
- exports to WAV
I've only been using it a few days, but so far it seems pretty good. I'm still new to the binaural beats thing, but I'm interested in seeing if it can help with dream recall/lucid dreaming.