Next issue number or graphic novel which follows on from the events of House of M for the Xmen?

If I recall correctly, the 'Decimation' series of trades would be a good place to start. I have Decimation: Xmen - The Day After (pretty good) and Decimation: Son of M which follows Quicksilver and is pretty awesome. Think there are about another 3 or so tho can't remember what they are. Think one is about a squad of human-piloted sentinels.

Yeah its Decimation, and I think the only one Daycrawler is missing is: The 198

Deadly Genesis, Decimation: X-Men The Day After, End of Greys, New X-Men: Childhood's End and the first few issues of X-Factor (Vol.3) are probably the most essential reads after HoM. I was say check out Son of M just because it's honestly a good read.

But if you don't feel like getting into all those you could probably just read X-Men - The Day After and Deadly Genesis and have a basic knowledge of whats going on.