Here's as complete list of subraces as I can come up with, based on what the folks here have posted and my own sources, by campaign setting:
Mystara:
- Aquarendi (aquatic elves)
- Blacklore elf (magic-users whose culture I believe died out in ancient Blackmoor; placed in the Hollow World by the Immortals to preserve their culture)
- Ee'ar (same as the avariel of other worlds)
- Forest elf (the most common subrace; essentially the equivalent of high elves)
- Gentle folk (primite elves found in the Hollow World)
- Icevale elf (primitive elves found in the Hollow World)
- Savage Coast elf (native to the western lands of the Savage Coast, fully integrated into human society)
- Schattenalfen (evil shadow elf offshoot)
- Shadow elf (pale-skinned subterranean elves with a strong aversion to sunlight; recently conquered the forest elf kingdom of Alfheim; not really evil but very xenophobic)
- Water elf (pale-skinned, seafaring elves with a mercantile streak; primary inhabitants of the Minthorad Guilds)