Watch the Staying In One Position online guitar lesson by David Hamburger from Focus On: Standard Tuning Slide
Just like using only one pentatonic position to play blues in standard guitar playing, you can make a lot of music sticking to one slide position as well. By adjusting a note here and there by just a fret or two, you can tailor your licks to address the chord changes going by. This is the approach Duane Allman took, and raised to such a high art that he’s influenced just about every subsequent electric slide guitarist alive. And while Duane generally did so in open E, it works just as well in standard tuning.