So, I think I made an inquiry about this ages and ages ago.  Actually, I'm fairly certain that I did, and Hitori/Brandon helped me out a bit.  Never did follow up on it, but..... I was just listening to the Xenogears Creid album again recently, and it struck me how beautiful the Honma vocal pieces are.  The Mitsuda-backed arrangements undoubtedly play a significant role there, but it got me interested in wanting to hear her other works.

All I can remember is that she had a few albums out under the group Moonriders.  Does anyone know exactly what albums they've released?  Are they any good?  And are they at all readily available anymore?

Moonriders was (is?) Keiichi Suzuki's band. As far as I can tell, she was only very loosely affiliated with them, like singing backup on tours or something like that. She was in a band called Platinum Kit (プラチナ Kit). I got their second album, 夏ゆきの雲, and found it fairly underwhelming. Head over to http://www.hmv.co.jp and plug in the band's name; you can listen to samples from both of their albums, which are available for purchase, should you take a more favorable view than I.

She also had two solo albums, "Really?!" and "Elbow Girl", and was in a band called Adi for the last three of their four albums. I see something about a わかつきめぐみの宝舟ワールド image album, though I don't know how much of a role she played in that, and she was also in Vita Nova (the group that did Orrizonte), though in a lesser role (she only sang one or two songs per album--info on which ones at the links here, and you can listen to samples at HMV), and it's not great, IMO, though your tastes may differ.

Ah, I vaguely remember hearing about Platinum Kit.  I just gave both of their album samples a listen, and I'm rather liking them.  Platinum Republic sounds a fair bit more upbeat than the laid back and breezy 夏ゆきの雲, but Honma's performances in both are quite nice.  I think I'll give them an order.  Thanks, Brandon!