Audacity is the tool everyone should start with to learn: http://web.audacityteam.org/. It not only receives input from your sound card but also audio interfaces such as http://www.sweetwater.com/store/detail/US16x08 which can send 8 signals/channels, not just 2. So you can mix 8 channels down to stereo. It is the recommended tool for PODs or audio blogs.
Reaper is a DAW or digital audio workstation software http://www.reaper.fm/. There are others but this one is not only a great starter tool, it is the most cost effective DAW I am aware of. Here is more info: https://en.wikipedia.org/wiki/REAPER
Online are many guitar tab files that you can not only read, but are animated and you can hear the music through attached midi files. The two main tools for reading and playing these files are: http://sourceforge.net/projects/tuxguitar/ and http://www.guitar-pro.com/en/index.php
Hydrogen is a great and fairly easy to use software drum machine. It is also a midi device, so it can receive events from you controller http://www.hydrogen-music.org/
JACK on windows http://jackaudio.org/faq/jack_on_windows.html. It connects audio and midi using system drivers. kind of a software patch board. It is new to windows but has been on Unix OSs (Linux, OSX) for years