i refer to this page often when trying to figure out which needle i need:
http://www.taunton.com/threads/pages/t00185.asp
make sure to read all the additional pages the little links lead to. pretty useful stuff. :P
here's another page from my favorites. i don't buy here, but this is also a great reference for needles:
http://www.shiboridragon.com/Notions.htm
someone sent me a very generous gift last year - a box of really expensive threads. some were $9 per spool. i'll always be greatful, of course. it was such a wonderful thought. i always get a warm and fuzzy when i load it onto the machine. the thing is, the thread i bought from threadart.com for a fraction of the cost performs just as well. and ... believe it or not, one of my machines works best when i use the dirt-cheap store brand polyester from walmart. (which, naturally, i didn't figure out until i'd spent a small fortune on the fancier stuff. go figure. :lol: )
experiment with the different threads available. buy only one or two at a time until you find the one that works best for each purpose, then WRITE IT DOWN or you'll have to start the search all over again. (don't ask how i know that. :lol: )