Sometimes if it's windy I tell myself "i am a leaf on the wind" (sometimes I'll say it out loud)... though I know that didn't end well in the movie, it mentally calms me down. I have done the same "BRING IT ON" stuff that others have mentioned if the conditions are nasty (I've done that running, too, and mentally it's helped).
I talk to my bike a lot. Sometimes I'm concerned people are listening. Mostly I don't care. ;) It's usually encouraging stuff, like "we're doing great" or "we're almost there" or "let's do this hill." If I say it out loud, it has to be positive. Sometimes if I'm riding with others who are behind me (or I pass) or need to be "pulled" through difficult terrain (hills, wind) I'll talk to them, too, but I don't want someone to feel like I'm talking "down" to them. Sometimes normal conversation, too, but that's usually just a distraction, albeit often a welcome one.
Sometimes I sing "she'll be comin' round the mountain when she comes" when riding hilly terrain. It makes me smile. I always imagine people coming out to meet me and all kinds of silly stuff.
I do make up songs sometimes, or make up songs to the words of other songs. One day when I saw a snake, I was making up a "badger, badger, badger badger, mushroom mushroom! oooh it's a snake!" song (a web video on weebls-stuff.com) except with marmots, snakes, and something other than mushrooms that took me a while to figure out (thus I sang the song for multiple miles of distracting enjoyment, and here I can't even remember what I substituted for mushrooms).

