My girlfriend bought some lychee the other day and I was wondering if
it's possible to get something from it . Can I use the same technics
as for the avocado seed ?

Google shows:
http://forums.gardenweb.com/forums/l...252229948.html
http://www.lycheesonline.com/faqs.cfm
http://www.crfg.org/pubs/ff/lychee.html

So it seems like it might work (and since you say you aren't hoping
for fruit, that simplifies things). One of the above links does say
you need to start it right away, and not let it dry out.