Per the buckler description (Player's Handbook 124), a buckler is strapped to the forearm. As such, it's pretty easy to equip two on a character with two arms. (Fun note: with the spell girallon's blessing (Spell Compendium 106) and the spell permanency according to Savage Species (60), some normally human-shaped creatures can tote four to six bucklers depending on their size and caster level.) Unfortunately, per below, there's no way to stack the shield bonuses from different bucklers to a creature's Armor Class. Also, per the description, although the buckler explicitly leaves the hand free, the hand possesses slightly limited motion: a creature bearing a buckler makes attacks with the buckler arm's hand at a −1 on attack rolls.
Per the section Combining Magical Effects (PH 172), bonuses of the same type don't stack unless explicitly stated. As such, a creature would only benefit from one shield bonus, like from a lone buckler. On the plus side, the most beneficial AC bonus of all the creature's bucklers is used. (For example, a creature bearing a +1 buckler and a +3 buckler automatically receives the benefit of the +3 buckler.)
A magic shield must have at least a +1 magical enhancement bonus before it can have other magic shield special abilities, such as death ward. Per the previous paragraph, only the highest enhancement bonus will apply, but there's no reason why a creature wouldn't benefit from different special abilities on different bucklers. In particular, there are magic shield special abilities that work on either armor or shields, so it's definitely true that you can simultaneously use abilities from different defensive equipment on different defensive equipment. However, it's also true that any bonuses from the same source don't stack, meaning two identical magic shields are effectively the same sources, and that's, effectively, the same as wielding only one of them.
As a side note, if just going for the Armor Class, you want the bonuses as evenly spread as possible. (Cost increases by the square of the effective enhancement bonus bonus.) If just pursuing Armor Class, trying coupling the magic buckler with a +1 or more defending dagger in one hand and a bunch of +1 bucklers.
And on a final, hopeful note, the book says (emphasis mine) "You can't bash someone with a buckler," which means you can bash someone with two bucklers.1
1 I know you can't actually bash someone with two bucklers, either. Sigh.