And now for the two reds:
This grape, crossed by Mr Kraus, a giant of Czech enology and the founder of the eponymous winery seated in Melnik, some 20 miles north of Prague, is a crossing of St Laurent, Blauer Portugieser and Alibernet (which itself is a crossing of Cabernet Sauvignon and Alicante Henri Bouschet). It combines the characteristics of these wines: the tannins and the edginess of a Cab Sauv, and the fruitiness and juiciness of a St Laurent (which is a Pinot grape). It has nice acidity and is fruity, but is a medium-bodied grape. It is successfully grown in Prague, too (by the Salabka winery).
Again a typically Moravian red crossing that combines the characteristics of Cabernet Franc (spicy, heavier paprika tones) and Zweigeltrebe (fruitiness and an easy-drinking character). It produces medium-bodied wines that are known for a nice blend of spicy and fruity notes. Look for bottles from the Slovacko region (Benes or Glos wineries in particular).
Where to have them?
That's easy. The biggest selection can be probably had at the Vinograf wine bars (they have two branches - a small, intimate one near the Charles Bridge, and a bigger one in the New Town area). If you wish to taste strictly organic wines (called "bio-dynamic" here) from the Czech Republic, definitely visit Veltlin, a fantastic and popular wine bar in the Karlin district. Finally, some fine dining restaurants in Prague may have a great selection. We know that the good people at La Degustation really take great pride in serving Czech wines, for instance.