So welcome to the new Infinity sub-forum. I asked for this sub-forum so that we can organize the first Infinity Campaign here.

First up a collection of links for new Infinity players. Once of the nice things about this game is that the rules and profiles are free. You pay for the Fluff, not the ability to play the game.

Corvus Belli Website: http://www.infinitythegame.com/infinity/en/
Corvus Belli Download Page: http://www.infinitythegame.com/infinity/en/downloads/
Official Infinity Forums: http://infinitythegame.com/forum/
Infinity Wiki: http://infinitythegame.wikispot.org

You can grab the rule books and profiles from the Infinity downloads page.

An alternate to the CB rules downloads is the unofficial re-edited rule book. This Indexed and Bookmarked PDF combines all of the available Rules information from the Infinity Rule book, and the Human Sphere Rule book. It is easy to navigate is what is most often used at the table. This download is much better organized than the official rule book.
http://wargamingtrader.com/infinity-rules

Army Builders
Devil Team 4.0 is web-based: http://www.infinitythegame.com/army/army4.php
There is also Aleph. You can grab this for Android and iOS (I think). There is also a browser based plug-in for Google's Chrome browser.