I've also found the Microsoft Works product to be sufficient for low resource computers, students and even for general office use. It's less than $60 and you get word processing (fewer features than Word but enough for most folks), a spreadsheet (likewise in relation to Excel), a database that meets most people's individual needs (not for network use), calendar, address book, etc. The file formats are (mostly) compatible with the regular Office products.
If you want all the above plus the full version of Word, Microsoft Money and more, you can splurge on Works Suite for 110 bucks.
Since most people don't use all the features in Excel and only occasionally use PowerPoint, the above should be sufficient. I consider these good values from Microsoft and often overlooked.