In 3.5, I can't hide if I'm visible, but does this include visible from allies but invisible from enemies?
And what about visible for one enemy, but concealment from another, can I hide from the enemy I have concealment for? Do I roll hide per enemy, or do I make one hide check for everybody?
On top of that, if invisible comes into play, do my allies still know where I'm hanging out?
Consider the spot check from anyone (friend or foe) with line of sight to be visible. Anyone with an obscured view must roll their spot against one hide check from the hiding character, which stays the same unless they perform an action (move or standard. Free actions are iffy). If you are using a map, LoS matters and circumstantial bonuses can be added to your hide check relative to the spotter. If your group doesn't use a map, you can abstractly track everyone but use a blanket circumstance modifier and unless there's a good reason why not, consider those who pass to be on one side of the room and those who fail on the other.
As far as invisibility, your allies don't instinctively know where you are. Many a game as been made hilarious by an invisible party tripping over each other, especially with mass silence cast.
