I've been reading a lot on how to get good orange flavor into beer on another thread about Blue Moon. General consensus seemed to be that the best option was dried sweet orange peel. Not as common as bitter orange peel, but it can be found both at homebrew suppliers and regular grocery spice aisles - McCormick's makes a line of it with valencia oranges. Add this with 10 or 15 minutes left in the boil. Next best option is the zest of three or four oranges soaked in 1/2 cup of vodka. Add this at flameout or add to the primary before pitching yeast - you don't want to boil it because the volatile essential oils will be lost. I've also read good things about really strong orange flavor by adding some zest (zest taken after soaking the oranges in star san for a few minutes) to the bottles at bottling time, but that seems incredibly tedious. Last, you could add some orange extract at bottling. As you might expect, this is reported to impart an assertive but weird artificial flavor.