The House is preparing to vote on a CR that incorporates a one year delay in implementation of Affordable Care Act (aka “Obamacare”).  This outcome almost assuredly guarantees a government shutdown. 
WaPo has a nifty page that summarizes the department by department impact.
In addition to the disruption to government business and the economy, there will be a cost to shutting down and restarting government operations, somewhere in the neighborhood of $2 billion, if previous episodes are a guide .
One interesting point is that the shutdown will be more widespread than in 1995-96 because this time around none of the bills for funding the various departments have been funded.
Hope you weren’t planning to visit a national park, museum, or get a new passport.
Final point for the confused: This is a separate issue from the debt ceiling, which will likely be breached around October 17.