For interpolation you will need to convert your LAS data to a terrain feature class. Unfortunately, I am not aware of filtering or classification algorithms available in ArcGIS without 3rd party extensions.
Here are some lidar processing software options that you may want to investigate.
FREE
ALDPAT
http://www.csc.noaa.gov/digitalcoast/tools/aldpat/index.html
FUSION
http://www.fs.fed.us/eng/rsac/fusion/
Multiscale Curvature Classification (MCC)
http://sourceforge.net/apps/trac/mcclidar/
COMMERCIAL
LP360 for ArcMap
http://www.qcoherent.com/
Toolbox for Lidar Data Filtering and Forest Studies (TIFFS)
http://globalidar.com/default.aspx
VG4D Production Manager
http://www.virtualgeomatics.com/solutions2.html
VLS lidar Analyst
http://www.featureanalyst.com/lidar_analyst.htm