There was a question about how ritual spellcasting (for clerics, wizards, and any other caster who's taken the appropriate feat) works. I checked the SRD, and it's definitely not presented well there. Unfortunately, the SRD is a bit too curt sometimes compared to the actual rulebook. For those of you who do have the rules, it's on page 192. Essentially, ritual casting allows the caster to come up with a free-form, non-combat use based on one of his or her spells. For instance, one of the examples given in the rulebook involves the PCs getting stuck with a powerful evil artifact that's too dangerous to use or get rid of. So the party's wizard creates a magic-item-destroying ritual, using acid arrow as the spell to power it. If you want to create a ritual, you need to explain what you're trying to accomplish and which spell you're using. The GM will decide how long it takes and what items you'll need; obviously, the bigger the effect you're going for, the longer it will take and the more unusual items you'll need. You cannot cast other spells while you're doing the ritual. When the ritual is completed, the spell you used is expended until your next full heal-up. You will need to make a skill check to successfully complete the ritual. In general, a failed check means the ritual still goes off but has unintended side effects. Three other things to keep in mind: Rituals are for non-combat effects only (sorry, you can't use one to kill your enemy from far away). Rituals are not repeatable -- they're meant to be big, complicated magics you pull out once in a while, not a regular part of your arsenal. And the requirements and effects of one ritual are not a precedent for future rituals.
