Wonder...just wonder...a little loittering perhaps...
Haven't really seen one, but doesn't mean there isn't one. Start with the large "known" landmarks. Museums, Churches, parks, plazas, neighborhoods (Salamanca, chueca, nuevos ministerios (bernabeu) ...then look into current works by knows architects....abalos y herreros, Jean Nouvel, MVRDV, Chipperfield...here's a simple map I found online: http://www.gomadrid.com/images/madrid.pdf
I will try to ask our Madrid office for any info they recommend.

thanks

you can not miss:
-the new Centre reina Sofia by Jean nouvel
-the new installation of the Museo Thyssen Bornemisza
-the Kio towers at Puerta de Europa
-skyscrapers along paseo de la castellana
-Palacio de Cristal inisde the Parco del buen retiro
-Palacio Real, one of my favourite

skip the Prado musuem, absolutely a disappointment

i second the Parco del Buen Retiro.... love that damn park...
morrocans are also very welcoming in that park.. hehe :)

i think one of the more interesting and important works of 20th century architecture in madrid is the Gimnasio del Colegio Maravillas by Alejandro de la Sota (C. Joaquín Costa, Metro stop- Nuevos Minesterios). a modest yet striking building, great integration of structure and light, interesting facade.

The torres blancas by Francisco Javier Saenz de Oiza is an interesting project--the address is Av. De América, 37.... try to see if you can go inside. a sort of utopian concrete fantasy-land.

a couple of newer projects that i thought were good are the channel-glass clad Centro de Archivos Regional, el Aguilar by Mansilla+Tuñon, in calle Ramirez de Prado; and a beautiful rehabilitation of las Escuelas Pias en Lavapiés (lavapies metro stop) by Jose Ignacio Linazasoro.

have fun in madrid!

There is a nice enric miralles project a block from PLaza de Roma (just east) on Calle de Alacala. It's a small photo gallery/ lecture room. One of his very early works.

You might want to get the book "Architecture Guide: Spain." Has addresses and info. They reprint every year or two. The 2002 edition had this miralles project. You can find it at any Corte Ingles.

Mirador Housing project by MVRDV

I second the Archivos Regional by Mansilla + Tunon. It was
a beaurocratic mess to gain full access, but well worth it.

Also, isn't Navarro Baldeweg's Teatro de Canal almost finished?