Familiars

[Cranthis]

So, I'm taking obtain familiar, and Improved familiar, and one of my group says that you can get a familiar not on the list of improved familiar. I believe him, I just can't find anything that gives rules on what can and can't be a familiar.

[Blue Lantern]

There are a bunch of feats equivalent to improved familiar, exalted familiar from BoED, Draconic familiar from draconomicon and improved familiar from Complete Warrior comes to mind.
Apart from that I am not aware of any rule about getting a different familiar and I believe is mostly about asking DM permission.

[Gnaeus]

Srd Says:
"The list in Table: Improved Familiar by Alignment presents only a few possible improved familiars. Almost any creature of the same general size and power as those on the list makes a suitable familiar. Nor is the master’s alignment the only possible categorization. For instance, improved familiars could be assigned by the master’s creature type or subtype,"

But of course, since the rule is undefined, in practice it goes back to "Ask the DM"

[Cog]

Improved Familiar saw reprinting in a number of books, usually with an additional list. I don't know if anybody's compiled all the options, but you might be able to track one down.

[eggs]

This (http://brilliantgameologists.com/boards/index.php?topic=7508.msg246875#msg246875) is the relevant post in the familiar's handbook.

It's also an area where you can pretty easily houserule extra creatures in without breaking anything.