A small handful of (probably non-exhaustive) lists for you, containing the class, the level at which you get the ability and the book it's on... It's worth noting that Mettle is an extraordinary ability for some and a supernatural ability for others: it won't matter most of the time, but it could come up in some corner-cases, particularly if your DM is fond of antimagic effects.
Base Classes that grant Mettle (Fort or Will partial reduced to no effect on successful save):
Hexblade 3 (Complete Warrior)
Extraordinary ability.
Crusader 13 (Tome of Battle)
Extraordinary ability.
Prestige Classes that grant Mettle:
Vigilante 9 (Complete Adventurer)
Extraordinary ability.
Pious Templar 1 (Complete Divine)
Supernatural ability.
Base Classes that grant Evasion (Reflex half reduced to no effect on a successful save if character is in no armour or light armour):
Monk 2 (PHB)
Ranger 9 (PHB)
Rogue 2 (PHB)
Ninja 12 (Complete Adventurer) *
Scout 5 (Complete Adventurer)
Swordsage 9 (Tome of Battle)
Prestige Classes that grant Evasion:
Shadowdancer 2 (PHB)
Dungeon Delver 4 (Complete Adventurer)
Halfling Outrider 7 (Complete Warrior)
Master Thrower 2 (Complete Warrior)
Extreme Explorer 2 (Eberron Campaign Setting)
Classes that grant similar or complementary abilities to Evasion:
Divine Oracle 2 (Complete Divine) **
Kensai 5 (Complete Warrior)***
Hmmm. That took longer than I thought it would! I haven't gone through everything; in particular I've missed out most campaign-specific stuff and the "Races of the X" books, so there could be more instances in those.
__________________
* A Ninja's Evasion can only be used when the character is wearing no armour
** The Divine Oracle's ability is called "Prescient Sense": it's an extraordinary ability almost identical to Evasion, but works in any armour so it's even better.
*** The Kensai's Withstand ability allows you to substitute a Concentration check in place of a Reflex save. If you have Evasion or Improved Evasion, it applies to the result of the Concentration check.