The examples are no longer pre-built in the SDK. To try out the Native Client examples right now in your Chrome web browser, please see the SDK page on GoNaCl.com and download the SDK examples from the Chrome Web Store.
If you would like to build and run the examples within the SDK then run these commands, starting from the examples directory:
cd %NACL_SDK_ROOT%\%NACL_TARGET_PLATFORM%\examples
scons
cd %NACL_SDK_ROOT%\staging
httpd
cd $NACL_SDK_ROOT/$NACL_TARGET_PLATFORM/examples
./scons
cd $NACL_SDK_ROOT/staging
./httpd.py
Happy hacking!