Any class restriction? Because Bards, Skalds and such can do this:
Pageant of the Peacock (Act, Dance)
Your elegant movements cause you to seem to be more than you are.Prerequisite(s): Perform (act) or Perform (dance) 4 ranks.
Cost: Feat or 2nd-level spell known.
Effect: By gracefully weaving your body through subtle forms and postures you can convince others of your breeding, eloquence, and refinement. For the duration of the effect, you gain a +4 circumstance bonus on Bluff checks, and may attempt a Bluff check in place of an Intelligence check or Intelligence-based skill check.
The subtle changes in your movements also confer a +4 circumstance bonus on Disguise checks to appear to be someone of a higher station (an aristocrat, merchant prince, or even a queen).
Use: 1 bardic performance round per 10 minutes of the effect's duration.
Activation: 1 standard action.
A Lore Shaman can get:
Benefit of Wisdom (Ex): The shaman relies on wisdom rather than intellect to gain and retain knowledge. She can use her Wisdom modifier instead of her Intelligence modifier on all Intelligence-based skill checks.
Which could be useful depending on the class you play.
Headbands/belts of mental/physical stats increase ability scores (and therefore ability checks as well). Buff spells can increase a stat as well (but do not stack with the headband/belt of the same stat).
Circumstance bonuses can also be applied to any check, I recommend that if a character "reads a specific book" or "consults an expert" or "Ritually prepares themselves" or the check "is in line with character background" you grant them a +1 to +5 on their next related check.
Circumstance bonuses are subject to GM discretion.
I had the same question - Inexplicable Luck is the only thing I found that really works if you want to have a 0% chance of making your character unusable for however many weeks.
Inexplicable Luck has so many uses, two feats may seem like a lot but it's a huge benefit. +8 to that important saving throw, +8 to that CL check to penetrate SR of the BBEG, etc.
The only other things I know of:
Good Hope
Stone of Good Luck
If you can get the Ancestral Memory spell - possibly via scroll/UMD if you're a sorcerer or wizard - you can get a nice +5 insight bonus on intelligence checks, besides a % chance of simply knowing the right answer.
The spell good hope or a laurel of command can get you a +2 morale bonus to ability checks. A luckstone provides a +1 luck bonus to ability checks.
An Investigator's Inspiration can be used to boost ability checks (and can be acquired through Amateur Investigator if you like). An 8th level or higher Void wizard can generate an aura that includes a +2 insight bonus to ability checks.
Ancestral memory unfortunately only grants a bonus to intelligence based skill checks, not ability checks.