Through February 1, 2010, Sinevibes has a free loop collection for you, Basslines:
Basslines is a comprehensive collection of acid, synth and bass loops developed for the most passionate music makers. Analog and digital basses, acid lines, pulsating and rhythmically modulated synths, robotic grooves – this sound library delivers professional-grade materials which will instantly inspire great new ideas. Contents: 200 bassline loops.
They’re also offering a free loop library, Ambisphere, with any purchase.