I will be traveling in Spain 18 - 31 December starting in Barcelona then to Granada, Sevillle (over Christmas Eve and Day) and finishing up in Madrid (with day trip plans for Toledo and Segovia).

I am familiar with the Christmas Market tradition in of other European countries. Are their holiday traditions (market or otherwise) that I can look forward to during my trip?

January 6th when Spain celebrates Fiesta de Los tres Reyes Mages (The Festival of Three Kings) is much bigger than Christmas Day.

Midnight Mass is important to many on Christmas Eve followed by a large meal. Gifts are small.

If there are shops dedicated just to Christmas, I must have missed them.

Don't miss the Christmas market of Santa Lucia, Plaza Nova in front of the cathedral. It is entirely devoted to "crèches" and Chritmas decorations and closes on December 23.

Feria de Santa Lucia is in Barcelona !

Christmas lights in the streets.
In BCN you will find a lot of Caganer figures for sale.
Placa Santa Maria del Pi is a market selling traditional food.
Every restaurant in Spain seems to close between midday the 24th until the 26th. So if you find a restaurant open boo it quickly.
The Catalans also take the 26th as a public holiday where as the rest of Spain does not.
City can have Christmas markets and these can be found by an on line search.

Yes, how could have I forgotten the caganers.

The misa del gallo (rooster mass) or midnight mass is something I've never attended in the 25 years I have been living here. My experience in Galicia was that we met up with friends for a few vinos before the Christmas Eve family dinner under strict orders to be home by 10pm. Every region is different, but here the traditional Christmas dinner for many families would be several kinds of local shellfish (velvet swimming crab, spider crab, shrimp, langoustine, goose barnacles, scallops etc) followed by delicious salt-cod baked with cauliflower and drizzled with ajada (olive oil flavoured with garlic and pimentón dulce) or a festive roast lamb/kid goat. I've never missed turkey and brussel sprouts to be honest. Many places hold a "mercadillo navideño" where you can buy handicrafts associated with Christmas. As IMDonohere says, Christmas Eve and Christmas Day are quite understated with the Reyes Magos (Epiphany) on January 6th being the main Christmas celebration, exchanging of gifts, the roscón de reyes (a type of festive cake) traditionally given to your godchildren. As January 6th is a public holiday, many people go out to party the night before.

People do go out on Christmas eve, to attend mass and then socialize with their friends, but take note that the vast majority of restaurants will be closed Christmas day, the first of the 12 days of Christmas, so plan accordingly.

Also, a lot of restaurants will be closed between Christmas day and New Years day so that they can celebrate the holidays with their families. And if you are interested in wine touring/tastings, most bodegas will be closed to the public during the same period.

One thing you may want to check out is the living nativity scenes, a tradition in Spain for more then 700 years. You'll be able to find a famous one in Buitrago del Lozoya, about one hour north of Madrid. Another famous one is in Bàscara, in the Alt Empordà (Girona), just south of Figueres.

Keep an eye out from the "caganer", which should be in most of the nativity scenes you'll visit, except for the living nativity scenes.

Caganer figures are disgusting, not "cute" at all.

I'd agree with the Belén or Nativatity scene-every a spanish town has at least one and some are quite elaborate. Don't miss trying the Torren or nugget with nuts that's a Christmas tradition.

I think caganers are pretty funny. We have one in our bathroom.

In Granada and Sevilla you should look out for the flamenco inspired villancicos (Christmas songs), often sung in the streets such as here: https://www.youtube.com/watch?v=uYRkHbpKygI.

Or more official, as here in the Sevilla cathedral: https://www.youtube.com/watch?v=8HOfmPmJTEQ

As anyone seen caganers anywhere besides Catalunya?

The ever discreet Caganers are great. Lighten up for God's sake. You'll find them in Valencia and Murcia too, and suprisingly, in parts of the Canaries. They go right back to the Baroque period, a clear example of the exaggerated realism associated with that style. 21st century caganers have honoured famous personalities such as Obama, Putin, Merkel, Pope Francis, Messi and Hugo Chávez. All manifestations of Caganers/cagonés should have UNESCO protection. Another eschatological Christmas figure in Catalunya is the 'tio', a wooden trunk that kids beat with sticks so it 'poops' candy. Delightful.

Thanks Mac.

Oh my, how fun! I just googled caganers Everybody poops...

On Antiques Roadshow last night from Myrtle Beach, there were some figurines from Germany in the 19th century that were similar. Nothing to do with Christmas or famous personages and with chamber pots. Still revolting.

An idea as old as time, lol.