Offimatic suites

MS Office is nice but expensive.

Alternatives (multiplatform):

+ OpenOffice (3.1.X stable; 3.2 crashes with DOCX files (no fix yet); 3.3 in RC phase) download

+ LibreOffice (OO fork in Beta stage; nobody is certain about Oracle intentions) download

Only for Linux:

KOffice
GnomeOffice

For Mac:

NeoOffice