This is a totally unofficial list that I originally put together over on the (now-defunct) Glorantha G+ group. So details may be wrong but a lot of this has been officially confirmed (e.g. that the product is planned, though not when it will be released).
I thought I'd share it here, for fun and info.
Even though the original post is several years old, I try and keep abreast of things and keep it updated with new products (and delete items when they're released). Input on this is of course very welcome, because I may well miss things (since I'm not actually Lhankor Mhy).
Please note - each section is not in expected release order, unless otherwise specified.
HeroQuest: Glorantha / QuestWorlds
The Dragonrise, the “offstage” material from The Eleven Lights, for HQG - Ian Cooper
Fonrit setting book for HQG - Ian Cooper
RuneQuest: Roleplaying in Glorantha (RQG) (updated 25/10/20)
Upcoming releases in likely (but not guaranteed) order:
Red Book of Magic - every Rune and spirit magic spell of any cult of any size in Genertela
Starter Box Set - including Jonstown setting and 14 pre-gens. This is aimed at existing players and not just those new to RQ/Glorantha
Equipment and Weapons
Sartar Book and Dragon Pass Gazetteer - now a box set
Cults Book and Prosopaedia - 100 long cult write-ups in two volumes
GM Book
Other RQ releases coming later on:
The RQ Campaign - along the lines of the Boy King campaign for Pendragon
Heroquesting
Upland Marsh
Pavis and the Big Rubble - by Robin Laws
Trollpak 2
Snakepipe Hollow
Holy Country (which might just be called Masters of Luck and Death)
Nomads of Prax- David Scott
Invisible God
Lunar Provinces
Other items mentioned in the past but not recently (so these might still be coming, or plans might have changed, and even if they're coming they could be way off):
Elder Races book - 12 races
Barbarian Town campaign pack - by Sarah Newton
Nochet - Harald Smith and others
Seapolis pack
Whitewall campaign pack
Heortland sourcebook
Kralorela sourcebook
Glorantha Quickstart booklet? - 48-page booklet, free PDF
Sun County (updated for the Hero Wars) - MOB
QuestWorlds (HeroQuest) publications
QuestWorlds Core Rulebook - Ian Cooper
QuestWorlds Worlds & Adventures book - how to create genre packs and adventures, with three sample genre packs and adventures, by Ian Cooper
QuestWorlds genre packs - various authors
Other Glorantha publications
White Bear & Red Moon board game - cleaned-up version of the classic board game
Nomad Gods - ditto, a cleaned-up version