Skill Replacement

[Zaq]

This is something that's relatively common in 4e, but not very common in 3.5, unless there's just a ton of options I'm not thinking of—which is the whole point of this thread. How many ways can we think of to replace one skill check with another? For example, Melodic Casting lets you use Perform instead of Concentration (specifically to cast defensively). I'll get us started with a few I can think of offhand, but by all means, please help me think of more.

Melodic Casting (feat, CMag): Perform instead of Concentration, but only for casting
Undersong (spell, SpC): Perform instead of Concentration, always
Word of Movement Sublime (Disciple of the Word class feature, ToM): Spend Stunning Fist attempt, use Truespeak for Balance, Jump, or Tumble [yeah, I went there]

Surely there's more out there. This is just a start, and I'll edit in more as you folks find 'em.

Note: I'm not looking for things that let you swap the primary stat of a skill. We have the X to Y bonus thread for that. What I'm looking at is wholesale replacing one skill with another, even if only under limited circumstances.

[Elfinor]

Some feats:
Versatile Performer (CAdv): When making a Perform check, you can subsitute (INT modifier) Perform categories with your highest-ranked Perform category. +2 Perform bonus when using multiple Perform categories.

Old Salt (Stormwrack): You can substitute a Profession (Sailor) check for a Survival check to predict weather. +1 bonus to Balance, Profession (Sailor) & Use Rope.

Some of the Skill Tricks in Complete Scoundrel allow you to make a Bluff check to cover a Diplomacy/Disguise failure - it's not exactly a substitution though.

EDIT:
Unnerving Calm (ToB): Substitute Concentration for Intimidate in a duel of wills. +4 on duel of will skill checks. +2 morale bonus on attacks (instead of +1) for one round on an opponent who ignores duel of will challenge.