You can look for people in
www.paginasblancas.es, but only if they have their phone number under their names and not private. But if they have their number with a company different from Telefonica (ONO, for example) they are not in that white pages.
The information numbers in Spain are 118XX. I've been working on one of them, and now I'm working in another one.
The cheaper from Telefonica phone is 11818, but they give you just a few information and think it's only in Spanish. The highest quality is 11811 (cheaper, with English, very polite). The most known is 11888 (very expensive, better English and other languages, not so polite and helpful). Never call 11824 because it's too expensive and the people are the same than in 11811. Every mobile company in Spain has its own number: Vodafone 11855, Movistar-Telefonica 11822 (bad, bad English, rude)...
11888 is the yellow pages number. If you look for a bussiness, they can't give you the number if the bussiness didn't pay to be in yellowpages. It's like QDQ number (11875), another guide.
The international numbers are: 11880 (from 11811), 11886 (from 11888), and 11825 (from 11822).
You can't dial this numbers from other countries, but you can dial them with your foreign mobile inside Spain.