House of M is either an Age of Apocalypse story, or will wind up completely changing Marvel
continuity. So you might just want to wait till its done to see what happens.
In other news: (and this will have spoilers for anything I can think of)
got that people? SPOILERS. ALL OVER.
Scarlet Witch went bonky and brought mayhem and destruction to the Avengers. Ant-Man2 (Scott Lang) and Jack of Hearts are dead. (Jack exploded, Ant-Man was at ground zero) Hawkeye is "dead". (zapped by an illusionary alien ship. surprisingly no body was found)and Vision was ripped into shreds by a rampaging She-Hulk and is being labeled as "dead".
The Avengers disbanded, Magneto took Wanda off the ruins of Genosha, where he's hanging out with Xavier and Wanda's powers becoming even more uncontrollable are what has led up to House of M #1. Apparently, Magneto is using her to remake the world to his specifications.
The "New Avengers" are together, and the team now consists of Cap, Iron Man, Luke Cage, Spider-man, Spider Woman, and maybe Sentry and Wolverine. Depending on if the first storyline ever ends.
The "Young Avengers" are a new team that claims to have been gathered by a Vision backup protocol to find the next generation of Avengers when necessary. The team is also still forming and currently consists of Asgardian (probably not one), Hulkling (revealed to be a shapeshifter), Patriot (the grandson of one of the original black Captain America prototype) , and Iron Lad (claims to be a young Kang, back in time to stop his evil older self)
Ant-man's daughter Cassie (Ant-girl?) and another chick combat-type (Hawkette?) are waiting to become members. The book is surprisngly entertaining.
I'm not fully caught up on the X-books, but they're just as complicated as always. Currently, Jean is dead again, Cyclops and his new girlfriend Emma Frost are headmasters of the school, Colossus is alive, and Squidboy is dead. I miss Squidboy.
Captain America got his series re-started at #1 again and the series is supposed to be good. I haven't read it yet, but I know that the Red Skull gets killed in #1, and other supporting characters get offed in future issues. The popular theory is that the killer mmight be Bucky. I bet its Toro.
Iron Man also has been re-numbered. But the new book never comes out and barely has Iron Man in it.
Thor fulfilled his duty and ended the Ragnarok cycle. Thor, and all the other Asgardians are dead. For now. Dollars to doughnuts he somehow gets reborn in House of M.
Spider-man has had his hands full with Gwen Stacy's kids. That's right, when she went to Europe back in the day, it was to hide the fact that she was pregnant with Norman Osborn's kids. What a dirty slut. Venom is also dead, and the symbiote had attached itself to Scorpion last I checked. It was bouncing around for a while. Carnage got ripped in half by Sentry in space in New Avengers. At least somethign good has happened.
The FF hung out with a human Galactus for a bit, and swapped Johnny and Sue's powers. But I'm pretty sure the status is back to quo in time for the movie. I havent read the last issue or two.
Hulk hasn't made any sense for a long time.
If you have any favorite 2nd string characters, current editorial policy is to treat them like dirt, kill them or ignore them. But I can try to answer specifics.