data preprocessing resources

I would start here:

http://www.burns-stat.com/pages/Tutor/spreadsheet_addiction.html

Then point the students to a basic tutorial about databases (or at least MSaccess).

Or you can have them enter the data directly into R without using outside products.  Some of the GUI front ends for R have spreadsheet like interfaces, or you can create an empty data frame with the correct column types, then use edit/fix to enter the data in a way that feels familiar to spreadsheet users, but prevents some of the major problems that come from abuse of spreadsheets.