It seems like whenever I get an erection, I start producing precum. The bonus is that--no kidding--I've never needed lube to masturbate, no matter how many times I've cum already that day. I just keep leaking until I've ejaculated. When I get hard again, more precum.
It's been a source of embarrassment before when I start to leak through my clothes (see picture) but it's also been a good source of excitement, particularly for some of my past partners. They've just
loved watching it drip out of the head and down my shaft. I've watched porn with some girls before who have always loved the fact that I'm always leaking lubricant when we're on the sofa and she's jacking me off.
Generally, when I find myself getting hard in public, I'll just automatically head to the bathroom and wrap my guy up in TP to keep from leaking through my shorts. One girl I met in grad school (and was friends with for several months prior to our relationship) who loved my precum told me that she had seen me leaking through my pants before in the hallway and had wondered if it was all precum. Needless to say, that got my dick leaking almost instantly. HOT!
http://www.lpsg.org/members/shr1125/albums/shr1125%27s+gallery+pictures/476484-img001253.jpg