PC98 Games Screenshot Project - Probably the most authoritative listing of PC-98 screenshots. Now that Ben has returned and filled most of it
out, it's a great guide for identifying games.
PC98 Library - A korean site which features both in-game screenshots and actual game cases, along with a short description, somewhat
like this site. While I don't believe it features quite the range of titles that the Screenshot project does, it has several titles that are
not listed there.
JRK's RPG site features RPGs and reviews for almost every platform imaginable, including the
PC-98 and PC-88. Text is in Polish, however.
AL32Gabby's PC-98 Page is a Russian page devoted to the system. Text is in both Russian and English, although
some menus are Russian only. He has a game list if you wish to trade games with him.
Sutorippu has reviews of a wide variety of adult games, including those for the PC-98 and PC-88.
Sogna Digital Museum is a site devoted to the now-defunct hentai game maker Sogna, which released most of their titles for the PC-98 as well as the standard PC.
FMV Forums are easily the best English (in the language, not the nationality sense) forums for discussing
PC-98 games and issues with people from around the world.