Portability.nl

First of all you need a Rooted device to rip applications !

* Install "Root Explorer" as provided within this ZIP file.

Note: You can do this by copying the .apk file to your sdcard and then tap the .apk with a file explorer that you probably already have installed.

*Create a folder on your sdcard named: "RippedApps"

* Start Root Explorer and go to /sdcard then longpress "RippedApps" and "Bookmark" this folder.
Note: This will help you make the appripping go a lot faster ;)
When installing applications they are stored in this folder: /data/app or /data/app-private
If you useapps2sd the applications will be stored in /sd/app or /sd/app-private

* Locate the folder where /app/ and /app-private/ reside and make this folder your “Home” folder by long-pressing the folder and select “Set as Home”
Note: The folder is most likely called /data/ or /sd/
TIP: Get your latest apps to show on top  of the view for easy access! Open your settings and hit "view” then select “Date descending”. You are now all set-up to rip some apps!

* Now open your /app/ or /app-private/ folder and (multi-)select the file(s) you want to copy.

* Select “menu” and then “bookmarks” and select the folder you previously bookmarked /RippedApps/.

* Now tap “paste” The application has now been “ripped” to your SD card and is almost ready to meet the world! Last thing you should do is rename the file to something that makes more sense, like: androidappname.v1.2.0.apk

Sidenote: When installing an app sometimes it splits itselves in both app and app-private folder.
Be aware of this, you only need the file in the app-private folder otherwise the install on a device won't work.

Sidenote 2: Do not try to send the apk files from /app/ or /app-private/ directly to your friends, that won’t work. The files MUST be copied to the SD card first !