Who conducted the piece that is preformed at weddings?

Question:I think you mean, composed rather than conducted. Pachelbel's Canon in D is another one of the most famous wedding pieces (in addition to the ones listed). It is also played at graduations.

Best Answer - Chosen by Asker: I think you mean, composed rather than conducted. Pachelbel's Canon in D is another one of the most famous wedding pieces (in addition to the ones listed). It is also played at graduations.

The one where the the bride walks down the isle?

The Wedding March by Felix Mendelssohn

there are several. The Wedding March by Felix Mendellsohn, the Brdial Chorus from the opera Lohengrin by Richard Wagner ( Here comes the Bride)
a couple of famous Ave Maria settings: by Franz Schubert and an arrangement by Charles Gounod on J.S.Bach's theme.
they are "performed" and were "composed" not conducted.
There are several standard wedding music books available at all music stores ( on line or not) or even at your local public library.

Tchaikovsky's Serenade for Strings is very common at weddings, though not normally when the bride enters.

Felix Mendelssohn's Wedding March is undoubtedly the most famous one.