What is a good declamation piece?

If I get you right, you are interested in the canto declamato, an operatic form where the length of the verse and the syllabic scanning design a high-profile, noble and fierce assertiveness in the characters. The ideal world of the declamato is Wagner's operas and the rhythm of the german language, although originally conceived in the italian opera environment. The early 19th century composers gave the best examples: Bellini ("Norma"), Spontini ("La Vestale"). To me, the best example of declamato is Luigi Cherubini's "Medea" and the aria that fully represents it is "Dal fiero duol", best if sung by Maria Callas. The version I am attaching is rather poor IMHO, but it just gives an idea.

http://hk.youtube.com/watch?v=wnZHdOTngR...

Do you mean a vocal piece in a declamatory style?

I'll look some up and post here in a little while.