I'd like to also point out that sentence relatives (another term for this category, thereby supporting Ed Vavra's contention that it sure would be nice to have some uniformity in our grammatical terminology)  such as "which" are far more prevalent in speech than in writing, occurring 13.6 times more frequently in spoken  discourse than in written, ranking as the #2 most common SLIP (Spoken Language Interference Pattern) (discourse particles are #1).
Which is why they probably sound so good and occur in newspapers.