Madison Blues is a three-disk box set released in 2003 of recordings from the post-Peter Green transitional period. It starts off with a set of four songs by Christine with the band with whom she recorded her solo record. The four songs are "Hey Baby," "It's You I Miss," "Gone Into the Sun," and "Tell Me You Need Me." Any list of all of Christine's songs should have those. (I personally think "Gone Into the Sun" is a great, great song.)
Much of the rest of the compilation consists of live recordings, some of which feature vocals by Christine. Some of the live songs she sings also appear as studio recordings, but there is one live song ("Lonely Without You") that to my knowledge isn't on any of her studio recordings, so I'd include that on a definitive list, too.
Here is some info on the comp:
http://discog.fleetwoodmac.net/discog.php?pid=403.
By the way, the compilation also includes that fabulous "lost" song by Danny Kirwan, "Purple Dancer."