Computer as amplifier?

If you have a sound card, that is properly configured, you don't need any software, just a hardware converter from the weak guitar signal to line level (used by the sound card).
You can convert the guitar signal with a mixer or any (multi-)effects pedal.

There are pieces of software, that will allow you to add effects to the guitar, but none, that I know, are free (or particularly cheap).

There are a fair bunch of free guitar modelers for the pc actually, but none of them sound particularly good. Remember that for any decent processor to work you'll need a soundcard that provides low latency, which more often then not requires proper ASIO support. As for sending the signal into your pc, you can also use a DI, the cheapest ones starting around $25 or so. Behringer has a DI with guitar sims build in for $39, the sound is very much like their GMX line of amplifiers.

http://www.behringer.com/GDI21/index.cfm?lang=ENG

Doesn't come much cheaper that this I guess.

Yes, a DI box would also work - I got one off ebay for €10.

The free recording SW Kristal Audio Engine http://www.kreatives.org/kristal/index.php?section=details
has function KRISTAL LiveIN that makes it possible to connect your mic/guitar and play thru KRISTAL using VST effect plugins in realtime.
And there is lots of free VST effect plugins, this is just some few http://www.kjaerhusaudio.com/classic-series.php

The PC ( together with a DI box) will then act as a guitar amplifier with an effect unit.

Kalle

I have been doing this for quite a while. Here is my chain:
Guitar to RV-3 (Reverb/ delay) no longer made but you could use any pedal.
RV-3 to A/B box (one to lap steel, one to guitar) The second wire off of the RV-3 goes to my regular amp.
A/B box to MobilePre USB (preamp) One channel is used for guitar the other is used for a microphone.
USB takes the siginal to the computer then through two M-Audio Studiophile DX4's.
This whole thing probably cost me about $400. There are also wireless headphones connected for the days when the wife has "had enough"

This give a very clear sound, no distortion. Since I mostly play lap steel and straight guitar through it I like the sound.
When I want to muddy it up a little I will run another pedal or a Korg PX-3 to give different sounds. You can also use various downloads from the internet to inhance your sound. I don't but have friends that do.

The most important thing is really the speakers. They need to handle the signal without breaking up. (headroom)

You can record through various programs with this and also use microphones to sing or record acoustic.

The last suggestion I would have would be to get a good music program. I use Band in a Box most of the time for back up. I also record with Power Tracks. Both of these are available from PGmusic.com.

There are a bunch of programs out there. It all depends on what you want to do. My son just ordered a new one that looks pretty cool. I just don't remember right now what it is called.

Have fun,

I use my laptop as my amp when playing at home as I have a Line6 toneport and a decent speaker system so I get some pretty nice sounds through it using the different amp modelling options. Also no messing around if i play something i decide i want to record as just load up a sequencer and its already setup.

I use a Line 6 Pod 2.0 and run my guitar through that into my computer then through my sexy speakers :D