/usr/google/appinventor/commands-for-Appinventor/adb: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory
Thanks to MadBoy over here for the answer which worked for me:
http://askubuntu.com/questions/74371/how-to-install-32-bit-version-of-libstdc-so-6-on-a-64-bit-machine/882292#882292
sudo apt-get install lib32stdc++6