Schedules can change, but this is how things look for the major orbital players as of today.
I put Orbital Sciences Cygnus/Taurus II in 2012 because while on paper for Dec. 2011 they've had problems that are likely to put them into 2012 - little things like one of Taurus II's engines burning up on the test stand & taking some of the stand with it
2011:
Dragon C2 cargo - ISS approach (optional C3 - ISS docking)
2012:
Dragon C3 cargo - ISS docking (if blended C2/C3 isn't done)
Dream Chaser drop tests (from WhiteKnightTwo)
Cygnus C1 cargo/Taurus II launcher first test flight - ISS approach
Falcon Heavy delivered to Vandenberg AFB SLC-4E
Dragon cargo to ISS goes operational - 12 flights
Cygnus cargo to ISS goes operational - 8 flights
2013:
Falcon Heavy first flight
Dream Chaser unmanned flight
2014:
CST100 unmanned flight
Dragon manned flight
Dream Chaser manned flight
2016:
NASA MPCV* unmaned flight (if NASA's SLS** booster is ready)
* Multi-Purpose Crew Vehicle - latest incarnation of Orion
** Space Launch System super-heavy lift rocket (70-130 MT)
I put Orbital Sciences Cygnus/Taurus II in 2012 because while on paper for Dec. 2011 they've had problems that are likely to put them into 2012 - little things like one of Taurus II's engines burning up on the test stand & taking some of the stand with it
2011:
Dragon C2 cargo - ISS approach (optional C3 - ISS docking)
2012:
Dragon C3 cargo - ISS docking (if blended C2/C3 isn't done)
Dream Chaser drop tests (from WhiteKnightTwo)
Cygnus C1 cargo/Taurus II launcher first test flight - ISS approach
Falcon Heavy delivered to Vandenberg AFB SLC-4E
Dragon cargo to ISS goes operational - 12 flights
Cygnus cargo to ISS goes operational - 8 flights
2013:
Falcon Heavy first flight
Dream Chaser unmanned flight
2014:
CST100 unmanned flight
Dragon manned flight
Dream Chaser manned flight
2016:
NASA MPCV* unmaned flight (if NASA's SLS** booster is ready)
* Multi-Purpose Crew Vehicle - latest incarnation of Orion
** Space Launch System super-heavy lift rocket (70-130 MT)