Of course they can be used in other laptops (they are not Dell RAM.... Dell get's them from 3rd parties), I usually sell stuff on my Uni marketplace or the trading post to cut the hassle, but ebay is the best option if you don't have options like that available to you.
BTW, a lot of people recommend you keep the Dell RAM just in case you have to send it in for a service... as Dell usually ships it back in its original configuration (ie: would raplace your RAM with the amount of RAM it came with). A way around that I suppose is to attach a note or something.....
stu