I still play 3.5 - does that count? (Your question specifies 3.0, but your thread tag is 3E/3.5.) We're currently running through two separate 3.5 campaigns, one on a roughly every-other-Saturday basis (that I DM) and one on a mostly-every-week-on-a-school-night basis (that my grown son DMs). Our Saturday sessions usually run about 4-5 hours, whereas the weeknight ones are built more for 2-3 hours. We stick mostly to the three core rulebooks for the PCs, with the DM allowed to reach out to other books as needed (usually for monster stats, but the occasional spell gets made commonplace in our campaigns, the best example coming to mind being the attune form spell from the Manual of the Planes). As far as 3PP, we've gotten the most use out of The Tome of Horrors and The Deluxe Book of Templates; otherwise, it's mostly WotC stuff. We haven't adopted a whole lot of houserules, other than your PC dies at "negative Constitution score" instead of -10, we most ignore Concentration, and we don't worry overly much about encumbrance.
Johnathan