driving from santiago de compastela to barcelona

Assuming you take the shortest route, which involves a lot of motorway, then I'd suggest these sites for stop overs, whether for sightseeing or for overnight: León, Logroño, Zaragoza and Lleida. I'm not including "smaller places", which might be equally alluring though. Have a look at the sites below and see if anything catches you eye along this route, so you can add to the places to visit. Logroño is land of good wines (La Rioja), and it's half way... what better place for an overnight, especially after having drunk a few :))

Tourism boards from the regions along the way:
Santiago de Compostela (Galicia)
León (Castille and Leon)
Logroño (La Rioja)
Zaragoza (Aragón)
and arriving into
Lleida and Barcelona (Catalonia)

and a map of these regions so you get your bearings.

thx for the quick response, Enric:) we would prefer smaller and more alluring places if you know of them:)

There are many, some will demand you leave the motorway for a few dozen miles. As said, it's best if you browse thru the sites I've mentioned and see if something interests you.... what's alluring to me might not be to you and vice versa.

If it was me ...

Day 1 Santiago de Compostela to Leon (with potential stops at Lugo, Ponferrada, Astorga)
Day 2 Leon to Pamplona (with potential stops at Burgos, Logrono, Puente la Reina)
Day 3 Pamplona to Barcelona (with potential stops at Olite, Zaragoza, Lleida)

or

Day 1 Santiago de Compostela to Leon (with potential stops at Lugo, Ponferrada, Astorga)
Day 2 Leon to Zaragoza (with potential stop at Burgos)
Day 3 Zaragoza to Barcelona (with potential stop at Lleida)

I think it will depend on your inertests. I am planning a trip going the other way (Barcelona to Santiago) and have pretty muxch settled on my stops. Bilbao seems an obvious choice for the first night, but I am not all that interested in Bilbao and opted for Santillana del Mar, a mostly intact medieval village. The cave of Altamira is a also a few minutes away. I also considered stopping in the Picos de Europa region around Potes, and am still considering adding another day in this area.

On the second night Pamplona is well located, but I am planning on a stay in Sos del Rey Catolico, another medieval village/hill town that is just a bit out of the way, and thus not heavily visited. I haven't been yet, but my impression is that this is very much like a Tuscan hill town, without the crowds.

There in Santiago, I'm sure you could pick up a map or guide for the Camino de Santiago. The driving route described in Rick Steves' Spain book includes a village stop at O Cebreiro. The coastal route is beautiful, as well, with both coastal and mountain scenery.

thank you all for your most helpful responses! we will drive to Burgos today and stay over; then to Lleida for another overnite and then to our destination, Perpignan. all of the suggestions were muchly appreciated:)