There are a couple, but they're not easy to get, especially as a cleric.
Easiest is actually the feat Easy Metamagic. Its from a dragon magazine, so not many people will allow it. It requires a metamagic feat with +2 or higher adjustment, and when you take it, choose any one metamagic feat. When you use that feat, it costs 1 less adjustment(To a min of +1).
Practical Metamagic is next. Practical Metamagic is only available to spontaneous spellcasters with the dragonblood subtype, and it does the same thing Easy Metamagic does. Its in Races of the Dragon(Or maybe Dragon Magic...I always forget which feats are in which).
There are classes out there that reduce metamagic. Incanatrix does that, and for clerics, Dweormerkeeper from CD web enhancement has it as a capstone ability as well. Though if you're using BreakGameMorekeeper, lowering metamagic is something small to worry about it.
Arcane Thesis can only be applied to arcane spells, but it lowers the cost of feats by 1(I believe it was errated to only apply to a single metamagic feat, wheras if you take it as is it applies to every metamagic feat on the spell. Not sure on that)
Metamagic School Focus is usable 3/day, and its probably the most effective way for a cleric to lower costs for metamagicking. It lets you 3/day lower the costs of applying metamagic to spell as long as the spell is from the school you specify when you take the feat.
The problem is, outside of easy metamagic, Extra Turning will be more useful to a DMM cleric than anything else for getting more DMM spells out there.