ProTools is generally recognized as the most powerful digital-recording software on the market. ProTools is expensive and very complicated, but it offers more features than just about any other guitar-recording software.
Adobe Audition is a quality alternative to ProTools. Audition is a little cheaper than ProTools and is easier to use, but it does not offer the same amount of options as ProTools.
Cakewalk offers software designed to specifically record your guitar. Cakewalk Guitar Tracks includes a virtual amplifier that allows you to create guitar tones by plugging your guitar straight into your computer. Cakewalk is great for recording guitar, but it is not as powerful overall as ProTools or Audition.
Audacity is a free audio editor and recorder. It only offers a fraction of the features that the more expensive software offers, but it is fairly simple to use and the price cannot be beat.
Kristal Audio Engine is another free guitar-recording program. It offers a few more recording features than Audacity, although it is slightly more difficult to use. Kristal Audio Engine, like Audacity, is a great way to start learning recording.