The simplest way is Airdroid
which uses your web browser to transfer files to both internal and external storage. Also there is File Expert HD
, a very good file manager with tools and many features. It does what Airdroid does and File Expert HD
has a built-in FTP server to transfer files. Both are FREE.
For more intermediate linux userrs there is Android SDK
. It uses adb to push and pull files from the internal storage and finally there is mptfs. These are linux apps.
Android drop mass storage support after 3.x or something. Funny, how google/android which uses a custom linux kernel can't make things easier for linux users with this MTP protocal.