OwnCloud is like Dropbox (Dropbox Clone), but Open Source.

Dropbox - Access, Sync and Share your data

OwnCloud - Access, Sync and Share your data, under your control

Task: Make a personal cloud server, school / Small Office Server, you can use own cloud, Raspberry Pi Own Cloud server is very small and simple. we can use solar charger / powerbank / Portable HDD / USB Stick we can use anywhere.

Own Cloud Function

• Mobile and Desktop syncing
• External Storage and Encryption
• Collaborative Editing
• Versioning and Undelete
• Galleries
• Activity Feed
• Calendars
• Contacts
• Application Store

Demo
http://demo.owncloud.org/

OwnCloud  Client

• Windows
• Linux

OwnCloud Mobile Client

• Android
• iOS

How to Install

1. Download Unix (.tar.bz2) or Windows (.zip) archive.
2. Check package integrity using MD5 (Unix / Windows) or SHA256 (Unix / Windows)
3. Verify the authenticity via PGP (Unix /Windows). The ownCloud GPG key is here.
4. Follow the ownCloud Admin Manuals’ installation chapter

1 Unix = Unix Operation System and Unix Like System (Linux)
2 MD5 / SHA256 check is file size or original file or hack-package 
3- Verify GPG for Original Download or Modify / Hack file 
4- I help for this step.

Now Download and test it.

btw who in hand Raspberry Pi. 

you have Raspberry Pi 

A) Install Linux OS after Web server, Database, PHP (Linux Apache2 MySQL PHP = LAMP)

B) Install OwnCloud Image on SD Card

http://sourceforge.net/projects/cloudstorage12/files/Raspberry%20PI/?
via Windows - Use Win32Imager and minimum 4GB SD Card
via Linux - use dd command and minimum 4GB SD Card

dd of=picloud.img if=/dev/sdb1 

more detail update later