I've never heard a guy bragging about doing a slut; to do so would be sort of contradictory.
There are certainly male sluts (man-whores) that I've met, who sleep around and blatantly lie to whoever they're dating at that time without any sense of shame. They definitely exist on the other side.
I think the double-standard of being a slut is somewhat justified though, since according to the laws of nature, a woman (assuming she is attractive) can have any guy she wants, and according to societal norms does not have to make the first move or "win over" the guy. For a guy it may be considered an achievement to put his moves down and get a girl, whereas women are simply expected to remain passive and respond to male advances. Add to this the fact that the majority of men have sex on their mind all the time, whereas the majority of women can control their urges to a greater extent, and the stigma of being a slut becomes understandable.