My favorite's:

www.bs-mm.com
for alot live performances and other stuff

www.britneyspears.com
it's not always quick with uploading, but it's the official site so all what there's written is true!

www.britneyspearsaddiction.com
it's a site with alot pictures, so if you looking for one, go there!

http://britneyspears.pagina.nl
alot links to britney spears sites. It's dutch, but there are site's in english, deutch and dutch. So just click one and you'll find out!

other one:
www.britneysdagboek.com
it's a dutch site.they quick uploading new news.