I carry mine OWB in a Kramer Scabbard holster under an untucked tshirt. I tend to wear most shirts untucked in the summer and this conceals very well when carried like that. I also have an MTAC IWB holster that works very well when I need to dress up a bit and actually tuck my shirt in. This is the Kramer Scabbard and my Ultra with thin grips:
I am surprised nobody has mentioned Crossbreed yet. I know the kholster is similar, but folks seem to prefer one over the other more often than not. Not to thread jack, but anyone carried a 1911 in a crossbreed?