Most multitracking software comes with plug-ins you can use on guitar tracks. However, if you are looking for plug-ins geared towards guitar you might want to look at some of the amp sim stuff like ReValver or Amplitube which will include dynamic processing and effects. DSounds makes stomp box style plug-ins designed for guitar. If you aren't set on doing it all in software, check out the Line6 GuitarPort (limited fx) and Pod XT (lots of fx and now with driver support for digital recording).
