Straight from the source: supremecourt.gov has the court calendar and docket; these will tell you what the court has done, current status of everything submitted to court, which cases have been resolved by opinion or order, which cases are up for argument, and which argued cases have been settled.

Scotusblog.com is also good: liveblog coverage of opinions and oral arguments, detailed post-argument analysis, detailed opinion analysis, tracking the relists, and an ongoing rollup of scotus-related news and opinion across the political spectrum.