Any alternatives for MS Excel?

I would like to suggest you to read the article closely related to your question, I hope it will help you to find the andwer to your question.

I don't know what managing project activities means... but I use Open Office, simply because it's not worth it to me to pay $200 for Excel.

Open Office does take some getting used to, and it's interface isn't as streamlined as MS Excel but it has most the features that Excel has.

OpenOffice is a full, free, open source Microsoft Office replacement that can open many files created by Microsoft Office. As the software’s compatibility is not officially supported by Microsoft, there are no guarantees that your files will work correctly, so there could be problems with anything but literal values and very simple formulas.

If you are talking about project management, there's Microsoft Project. That's better suited to managing complex projects with multiple participants, milestones, steps, time estimates, defining dependencies, etc.

There's always Microsoft Project. It's specifically designed to ease the project management administration.

http://www.microsoft.com/project/en-us/project-man...

Gnumeric:

http://projects.gnome.org/gnumeric/

Or Libreoffice Calc:

http://www.libreoffice.org/features/calc/