By the rules, it's 1 spell per scroll, 1 scroll per day.
My house rule is:
1 spell per scroll per caster level. Thus, a 3rd level caster could put no more than 3 spells onto a scroll.
Hasn't even really come up in my campaign yet, but it seems pretty reasonable to me. I've thought about modifying it to be one spell level per caster level, so that a 3rd level caster could scribe 3 1st levels, or a second level, or a second and a first, onto one scroll, to a maximum of 1000gp.