Neat. What's a mundane item's saving throw bonus? "even against attacks from which a nonmagical item would normally get no chance to save." implies there is one.
More amusing than useful, but Magic of Eberron has Impact Armor, which is armor that gives DR (3/piercing max, so not too exciting) in exchange for lowering your speed when you're hit. Complete Warrior has an enchantment called Anti-Impact which halves bludgeoning damage that effects most of the body (constriction and falling are the given examples). It's not particularly practical, though not especially impractical, to have Anti-Impact Impact Armor.
One that is useful right under it though is this
This mithral +2 chainmail armor was built by the elves for rangers on long-range patrols. In addition to its protective qualities, it provides the wearer with immunity to fatigue and exhaustion. Moderate Abjuration; CL 8th; Craft Magic Arms and Armor, restoration; Price 21,500 gp; Cost 10,900 gp + 848 XP; Weight 20 lb
Not easy to get immunity to both. You don't need to sleep unless you're a non-cleric caster, plus the obvious uses for Barbarians. I'm sure in Eberron this item is instead meant for meatbags keeping up with Warforged since "Elf Rangers on patrol" isn't really an Eberron thing.
Tome of Ancient Lore from Complete Divine has a 90% chance each day to hold any arcane spell. It's a relic so you have to take True Believer (or be a theurge to use it). Even if you can't copy spells from it (though RAW only the location changes so you can still work to understand it one day then copy it the next), using a normal spellbook for your staples and this to have a good chance of getting any situational spell you want is solid. This is especially so if you leave slots open and prepare them as you meet problems since preparing spells from it takes half the time.
the tome of ancient lore (and copies made since the original left Boccob’s library) is cursed with a deliberately confusing, everchanging system of cross-referencing. The pages within the tome rearrange themselves, apparently at random. Finding anything useful by browsing is impossible,
So it's basically Fantasy Craft
Complete Scoundrel has the spell Blockade, a level 1 spell that creates a giant thing of wood.
You call a cube of solid wood, 5 feet on a side, into being . The cube must be created upon solid ground in an empty square . If no solid surface exists that is large enough for the cube to fit on, or if no adjacent square is empty, the spell fails . The cube weighs 2,000 pounds . It has a hardness of 5 and 600 hit points, and it completely fills one 5-foot square . Multiple cubes can be stacked . If it is pushed into water, the cube floats . Material Component: A block of wood, less than 3 inches on a side.
Plenty of uses for a first level spell (Off the top of my head, it can block a door/narrow passage, prevent a target from reaching you with a charge, create cover, break weak floors, or jam room trying to crush you) and it will stay relevant for a long time. The 3 rounds minimum and maximum limits the creative uses, but the real nice thing is this takes only a swift action to use. This is a spell that would still be pretty decent if it was a standard action.
By contrast, it's impossible to cast the spell directly below it normally. Catapult requires the object effected be in your hands (plural) when you cast it but has an S in its component list. Any reasonable GM will pretend it said hand though the spell isn't that great even then it's not a great spell. First level would be reasonable (Pathfinder has this as a cantrip with worse range), but second level is a flat nope.
Evacuation Rune is a 5th level spell that lets you put an Arcane Mark on something and Greater Teleport to it as a swift action within the next 24 hours. It explicitly works if the object is moved. The obvious and intended use is as escape button functionality (for yourself only...), the easiest way to make use of this I can think of to abuse it is Planar Binding something with at will teleport for itself and 50 pounds of gear. That or making a hired Greater Teleport a little cheaper.
Magic item wise...
The aspect mirror is amazing! 4000 GP to communicate with any mirror in the set. Less than half the price of a Speaking Stone, much faster and better range. House Sivas? Who needs 'em?
Bladeshimmer makes item it is slathered on invisible, seemingly indefinitely (or at least till the oil is washed off). There has to be a way to abuse this.