A chosson frees the congregation with whom he davens from saying tachanun. What sources are there for this in the following tefillos: 1) Shacharis on the day of the wedding 2) Mincha before the chuppah (with or without the chosson) 3) Shacharis the day after the last sheva brochos (the 8th day, if wedding day is day 1).
1) Shacharis the day of the wedding, in the Minyan the Chassan is Davening in you do not say Tachanun (Knesses HaGedola Orach Chaim 131, Levush Orach Chaim 131:4, Shulchan HaEzer Volume 2 page 26b Seif Kattan 8). However there are those that say that the Congregation should say Tachanun at Shacharis, just the Chassan himself does not (Radbaz Volume 1 - 179)
2) Mincha where the Chassan is Davening - you do not say Tachanun. (Birkei Yosef Orach Chaim 131 Seif Kattan 5, Kitzur Shulchan Aruch 22:7, Rav Pealim 4 Orach Chaim 4, Shevet HaLevi 9, 256). Mincha in the wedding hall, even if the Chassan is not present you do not say Tachanun (Shulchan HaEzer Siman 7). Mincha at the house of the Kallah you do not say Tachanun (Shulchan Shlomo 131:4).
3) You do not say Tachanun for the Shivas Yemei Mishte - the 7 days of Sheva Brachos. This means from the Chupa 7 x 24 hours. http://hebrewbooks.org/pdfpager.aspx?req=46546&st=&pgnum=81&hilite=