In addition to LaTeX, a number of WYSIWYG (What You See Is What You Get) office suites have been written for Linux. The point of these suites has always been to provide compatibility with Microsoft Office. In the beginning, there were three closed-source office packages, StarOffice, ApplixWare, and WordPerfect office.
Over the years, ApplixWare and WordPerfect office gradually went away. StarOffice was purchased by Sun Microsystems and open-sourced. Also during this time, KOffice, the KDE office suite, and GNOME office have come out. So what started as three closed-source office suites has become three extremely capable open-source office suites.
OpenOffice is the open-source project based on the codebase of StarOffice, released by Sun under GPL. OpenOffice is the newest of the open-source office suites, but has the most mature codebase of the three.
KOffice was the first purely open-source office suite. It was developed to be the office suite for KDE, but works just as well with GNOME or any other window system. It includes a word-processor, spreadsheet, presentation program, a drawing application, and a number of other programs.
GNOME Office is easily the least-complete of these office suites. AbiWord, the word processor, and GNUmeric, the spreadsheet program, are already stable. By contrast, Achtung, the presentation program, is still in the design phase.