I had a spreadsheet (Excel sheet for you MS Office users) with over 253,000 entries. Since I run on Linux, I use OpenOffice.org's SpreadSheet program, which unfortunately supports a maximum of 65336 rows only.
A quick search got me to a comparison between multiple products that support more than that limit. OK, I lied. Two products only.
This Wikipedia page shows a nice table but people tend to overlook the tiny little IMPORTANT numbers used for special notes!!!
The products are: Microsoft Office 2007 and Gnumeric.
Unfortunately (yes, another unfortunate event), Gnumeric requires that you recompile it with max number of rows you desire. This can be a good thing if you look at it from the point that you can surpass the limit that Microsoft is boasting.
In all cases, opening such large sheets requires large memory. I'm guessing at least 1GB (for the data itself, not counting the program!). I'll test this claim on MS Office 2007.