You mentioned in another thread that you do some yoga.
Warrior II pose and Pigeon pose are great for the hips and my knees respond well to any gentle stretching of the quads and hamstrings.
If your job allows you to get up and move around at least once an hour, that might help--even if you need to make a not-exactly-neccessary trip for paper, scotch tape, coffee, etc.
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"Light it up, Popo." --Levi Leipheimer