This is very cool software for people who always need something to read when they think they are idle. You can store variety of documents, PDFs etc and view it in this software. One differentiating thing I found with this software is that it opens documents in your internet browser so you can rotate your phone horizontally and readability improves automatically.
To install Docs, you can search Docs either in Cydia or in Installer, whichever you like. And then install it.

Needless to say that you need to first jail break your iPhone to install softwares unless you are ready to pay and get it from iTunes. I have been searching and trying softwares for quite some time now and I thought it would be worthwhile to share my experiences with you.
Below is the list of software which I think can add a great value to your iphone ofcoure it is quite dependent on person and his likings and profile etc but you can always choose what you find interesting and ignore what you would hate.

1. SummerBoard
2. GRE Vocabulary
3. Call History Patch
4. MxTube
5. SendPics
6. Wallpaper
7. AgileMessenger
8. PhotoDial
9. weDict
10. Docs