Rueda and Ribera del Duero represent two amazing regions, with very different wines, that you will also find prominent at good wines shops.
Rueda wines are some of the bargains of the white wine world. Produced with a grape called Verdejo, they represent the modernity of the Spanish wine industry.
Ribera del Duero, on the other hand, is about history. The legendary Vega Sicilia winery is here, where some of the top Tino Fino (Tempranillo) is grown.
Rueda: Geography, Grapes, and Terroir
Wineseracher: Rueda (which outlines the changes to the laws and new grape varieties allowed), and Verdejo
Wine Folly: Wines of Rueda, Spain
Sevenfifty Daily: Rueda
Vinepair: The Wines of Rueda and Verdejo
Ribera del Duero: History, Vega Sicilia, and Terroir
Winesearcher: Ribera del Duero
Wine Tourism Spain: History of Ribera del Duero
Vinepair: 9 Thing to Know About Vega Sicilia
Rare Wine Company (Importer): Vega Sicilia
Vinfolio: Why you should collect Vega Sicilia
Wine Enthusiast: The Riches of Ribera del Duero (good list of solid producers)
Ribera y Rueda (yes, the two regions co-market): From the Somm Journal – on the ground in Rueda and Ribera del Duero (very good article!)