I thought I'd commented on this thread already, but I guess not. Great advice! Thanks B!
My girlfriend isn't into some of the stuff in here or it doesn't work well for her (every girl is different), but some of the advice I've put to great use and had amazing results. I tried the grinding during sex last night and she orgasmed 5 times through this alone and told me I blew her away, and just lay there afterwards saying "Oh god, oh god" for about 10 minutes.
Another tip I'll add to this is something I do regularly. Basically work your fingers extremely lightly and slowly over her body and thighs, gradually towards her cl!t, then starting rubbing lightly, teasingly moving away, then building up the focus and speed. Just as she's getting majorly excited and close to orgasm, slow down again or stop. Then start again slowly and build up, then slow down or stop. I do this several times and not only does it make the experience last a whole lot longer for her and drive her crazy to the point where she's begging me not to stop, but when I finally allow her to orgasm (note that I'm in total control) it's absolutely incredible! Then she literally begs me to fvck her and ends up having orgasm after orgasm!