If you're seeking a free alternative to Excel, simply install Apache OpenOffice and use the 'Calc' program that's built into it. (I've been using it earlier this afternoon and I can recommend it):
https://www.openoffice.org/
Most Microsoft Office templates can also be opened (and then modified) in Apache OpenOffice. e.g. the multi-week planner:
http://office.microsoft.com/en-gb/templates/results.aspx?qu=planner&ex=1&origin=TC102930028#pg:2|ai:TC001180164|
the monthly planning guide:
http://office.microsoft.com/en-gb/templates/results.aspx?qu=planner&ex=1&origin=TC102930028#pg:5|ai:TC101885859|
Alternatively in Microsoft Word (or any other word processor, such as OpenOffice Writer), simply open a new document. Go to File > Page Setup and select Landscape. Then go to Table > Insert > Table. Select 3 rows and 8 columns. Drag the bottom right-hand corner of the table down to get the table to fit the page. Leave the top left cell blank and then type Monday, Tuesday, etc across the top and Week 1 and Week 2 down the side (using the usual word-processing controls to adjust the font, positioning, etc. (Once you've experimented a bit you can use the table auto-formatting option to produce a much more elegant table).