Most Lego sets have building instructions for two models, sometimes three. Using some tricks there is sometimes a way to get more.
Now owners of the 5867 Creator race car can find instructions to build two special models. The instructions can be downloaded from the German Lego club page by writing "CLASSIC" or "TRUCK" in the clubcode field (all caps):
One can find more instructions on the Lego club page, for example the "Blue Lightning" that can be built from the four sets from 8192 to 8195.
As Easter is approaching there is of course room for nice small animals. Bunny & co. can be downloaded from here.
Lego recommends to get the bricks from Pick-a-brick.
Update: one of our readers has recommended Technic set 1030 from 1983 from which a lot of simple functions can be built. It has many typical parts that are easy to find in other sets. The instructions on Peeron are somewhat incomplete but he has provided a complete version that can be downloaded from here as a 6.5M PDF file (6.5M).