: Widely considered the gold standard for full, up-to-date MAME sets. They offer MAME 0.287 ROMs in merged, split, and non-merged formats. Internet Archive (Archive.org)
Support the developers where possible – many classic games are now available in official collections (Capcom Arcade Stadium, Arcade Archives, etc.).
For over a decade, the (now operating via various mirrors and torrent sites) maintained the defacto "top pack." They released curated, verified, full MAME torrents (ROMs + Rollback ROMs for high-score saving). Currently, successors maintain these "Split" sets, which are considered the industry standard.
The next "holy grail" for collectors is the Full Software List ROMs —which includes not just arcade games, but computer software for the Commodore 64, Amiga, and Apple II that MAME can now emulate. A true "all" pack now exceeds 1TB.