Autozone also carries a Castrol synthetic that is BMW Long Life certified. I use it as my dealer is not conveniently located.
Beware that you'll have the check the fine print on the labels carefully. Only one of the grades they carry has the LL certification. It also has a VW and Mercedes certification.
2012 E88 128i, Alpine White/Black
2011 E90 328i, Crimson Red/Black
2008 E60 550i, Carbon Black/Natural Brown, ED 2 November 2007 (retired)
2006 E83 X3, Silver Grey/Black, ED 15 May 2006. (retired)
2005 E46 330i, Jet Black/Black (retired)
2002 E46 325i, Electric Red/Black (retired)