R: regression data set

hi all

i am busy teaching a regression analysis course to second year science
students. the course is fairly theoretical with all of the standard
theorems and proofs...

i would like to give the class a practical assignment as well. could you
suggest a good problem and the location of the data set/s?

it would be good if the data set has been analysed by a number of other
people so that students can see the different ways of tackling a
regression problem. 

some of the issues to be covered:

estimation
is there really a model
variable selection ...
outliers and influential observations
interpreting the regression model


/
allan