"Palenque is the only major ancient Mayan city to which I have not traveled." --
milena_shibush Probably of interest to noone else here, below are the Maya ruins I've visited, as best I remember, in the order I visited them within regions. Some I've visited multiple times, but I only list them once.
Yucatan Peninsula: Chichen Itza, Kabah, Uxmal, Dzibilchaltun, Sayil, Labna, Xlapak, Bolonchen, Mayapan, Telchaquillo, Acanceh, Izamal, Etzna, Tulum, Balancanche caves, Xpujil, Becan, Chicana, Kohunlich, Akumal, Chacmultun, Ake, Coba, Loltun, Dzibilnocac, Dzibalchen
Chiapas: Palenque, Comalcalco
Guatemala: Kaminaljuyu, Tikal, Quirigua, Iximche, La Democracia, Zacaleu, El Quiche, Gumarcah ...I think I'm forgetting a few small ones in the Guatemala highlands. I flew into Tikal for a day, but otherwise have seen none of the Peten.
Belize: Altun Ha, Xunantunich
Honduras: Copan, Siboney/Calabasas, Campo Pineda, La Lima, La Travesia
Favorites: Copan, Palenque, Uxmal.
Major ones I've never visited (and would like to): Calakmul, El Mirador, Yaxchilan