How do I attach an EXCEL link attachment and people who do not have MS office view it?

I have a Spreadsheet (workbook) that has 18 tabs. I use a message board web site that has 14 people total. When I want to post something on the message board, it gives me an area to post an attachment. So I put my EXCEL spreadsheet in there by locating it on my computer through the "browse" feature. Good right? Well the problem I am having is not ALL 14 people have Microsoft Office XP or ANY form of Microsoft Office. Some of the people can view the information only because they have that trial period that all computers have for 30 days or whatever but my concern is, when that runs out, I still want them to be able to view the information on the spreadsheet (all 18 tabs). Some of the people can only read the FIRST tab that's on my spreadsheet. I tried saving my spreadsheet as "web page" but that didn't work, it showed all 18 tabs but the contents of each tab were "unavailable". I thought maybe saving it as a different format might allow them to open it. I tried converting it to a PDF file...that didn't work (only converted 1st tab and half the contents were cut off)

So my question is this... Does anyone know a way I can EASILY attach my spreadsheet to my message board where everyone can view all 18 tabs every time they open it w/ out having to use the TRIAL PERIOD or having to buy the $150.00 program? Thank you all for any help you can give.