Editors' Note: This is a development release for those who want the bleeding edge.
Gnumeric is a powerful and easy to use spreadsheet using GNOME. The goal of Gnumeric is to be the best possible spreadsheet. However Gnumeric can read files saved with other spreadsheets and we offer a customizable feel that attempts to minimize the costs of transition.Gnumeric handles large spreadsheets while remaining responsive.
Gnumeric will import your existing Microsoft Excel files. Import filters also exist for Lotus 1-2-3, Applix, Sylk, XBase, Open Office, Quattro Pro, Dif, Plan Perfect, and Oleo files.