That's a good start with the dumping project page. For some we'll need to clear up just what needs to be dumped. I know some FM Towns Marty games have been dumped and can be played in emulators, but does the entry means the real BIOS haven't been dumped? I'll try to add some more systems and more information when I get a chance.
Lately, I've been working on a list of undumped Japanese systems, with the intention of tracking some of these down with the help of Guru's Japanese contact. At least a couple of people have mentioned wanting to donate for MESS dumping, so this could be a good opportunity.
I'll start out with a list of completely undumped consoles/portables released only in Japan. In most cases, we'd probably need to find these to know how difficult dumping would be. (The 64DD is an exception, since no ones knows how to dump it, but I'll include it for completeness.)
My plan is to first run the list by the people here, in case it turns out something actually has been dumped, or something is missing. Then I can update the Wiki and send a list to Guru. Some of these have already been mentioned on the Wiki, but I've got at least a bit more information. Later, the effort can be expanded to partially dumped systems, i.e. figuring out what games still need to be dumped.
Bandai Supervision 8000 -- first cartridge-based original Japanese system, from 1979, not related to the Watara Supervisionhttp://darkwatcher.psxfanatics.com/console/supervision.htm
Epoch Cassette Vision -- 1981, Ian Knowles posted about having one, is it available for dumping? This was also updated as the Cassette Vision Jr. in 1983. A follow-on, the Super Cassette Vision, has been emulated.http://darkwatcher.psxfanatics.com/console/epoch.htm
My Vision -- 1983 by Nichibutsuhttp://darkwatcher.psxfanatics.com/console/myvision.htm
Casio PV-1000 -- 1983http://darkwatcher.psxfanatics.com/console/pv1000.htm
Gakken Compact Vision (TV Boy) -- 1983http://darkwatcher.psxfanatics.com/console/gakken.htm
Nintendo 64DD -- 1999, disk add-on for the Nintendo 64. Any idea how to dump these?http://64dd.emedian.eu/64dd.net/modules/news/
Casio Loopy "My Seal Computer" -- 1995http://darkwatcher.psxfanatics.com/console/loopy.htm
Pasago -- portable by Koei with carts based on famous Go tournaments, hard to find much info on this, not even sure about the year of release:http://assemblergames.com/wiki/dogatemysnes/pmwiki.php?n=Topics.KoeiPasagohttp://ultimateconsoledatabase.com/portables/pasago_go.htm
Bandai Telebiko -- obscure VHS-based system, not sure about the year:http://ultimateconsoledatabase.com/Morinfo/bandai_telebiko.htm