I love my Sci-Fi, especially hard sci-fi.
I would highly recommend:
Neal Asher (Gridlinked is a good one to start with)
Alistair Reynolds (start with Revelation Space)
Peter F. Hamilton (especially the excellent Nights Dawn trilogy)
Charles Stross
Iain M. Banks (especially the Culture books)
Dan Simmons (the Hyperion Cantos - starting with Hyperion)
Richard Morgan
A bit biased towards UK authors, but IMO thats where the best Sci-Fi currently comes from
Anthony