I am thinking to sell many domains I had a great idea for but never did anything with..but in the back of my mind is will I regret selling! A mental struggle.
It is hard to let them go especially if you had a development plan but never got the time in the last year to get it done. I have been trimming the fat lately too but I just renewed a bunch I had let go but decided to renew them even though they expired a few weeks ago. Still trimming your portfolio is a good idea.
Every seller comes to the point when they must make such a decision. For some it's easier since it's just business. For others, the decision may be tougher. Letting go of a dream/vision/idea is not easy. Anyway, take the first step. It gets a little easier as you get into the swing of things. . .
Don't list them on eBay like mentioned above for starters, you won't get their true value. As for whether you should sell, I've heard a lot of domainers say that the domain market is going to drop in a year or two so it might be best to sell now Don't ask me why they say this, because i don't know... I assume it's something to do with the acceptance of new TLDs like .info .biz etc. No one can predict the future though