When it comes to file sharing, one could argue that Dropbox is the most popular file sharing application. However, the Internet is crowded with all sorts of file sharing applications that offer similar functionalities as Dropbox. This list includes the following applications:

#10: Quazaa is probably the most complete P2P application. It supports four separate P2P networks:
eDonkey2000, Ares, BitTorrent and G2. However, it's worth noting that the project is in pre-alpha stage now.

#9: FrostWire is a bittorrent client which was released as a fork of LimeWire. It offers all the functionalities you might expect from a bittorent client such as:
  • Magnet links support
  • Online chat rooms
  • Internet radio support 
#8: RetroShare is an Open Source decentralized file sharing program. It lets you easily chat and share files with your friends.
RetroShare is serverless which means that you don't need to register to use the program. It also offers a high level of security by encrypting all connections.

#7: OwnCloud is a an Open Source web based application which you can install on your computer or server. It is a free cloud computing solution which offers a lot of functionalities such as:
  • File encryption
  • Versioning support
  • Music streaming
  • Todo list app
  • Etc 
#6: SpiderOak is a cross-platform online backup tool. It allows the user to synchronize any folder of his computer. SpiderOak offers a lot of features such as:
  • File encryption
  • Free 2 GB account
  • Versioning support  
#5: SparkleShare is an Open Source program which offers cloud storage and file synchronization features. It allows you to use either your own server or a hosted service such as GitHub or Gitorious.

#4: Wuala is a cross-platform file sharing application. It offers similar features as Dropbox.

#3: Minus lets you easily share files with your friends or family. It offers a 10 GB free sotrage space.
Minus provides a simple way to share files, just go to their website and use the Drag and Drop functionality to upload your files.
Minus is a cross-platform program, so you can use it to access your files regardless  of which OS you're using.

#2: Syncany is a server-independent file sharing application. Syncany is under active development and the official version hasn't been released yet but it will offer promising features such as:
  • Data encryption
  • Box.net: uses a Box.net folder as data storage.
  • Picasa Web Albums: encodes the file chunks in images, and uses a Picasa album as repository.
  • Versioning support 
#1: Drops is probably the most unheard of file sharing application. What makes Drops so special is the fact that it offers unlimited file storage regardless of which account (regular or premium) you are using. Drops also offers a cross-platform desktop application. Among Drops features are:
  • Web interface
  • Online preview of uploaded files