Which books are in AEG's Oriental Adventures product line?
The books in that line are the ones that WotC gave permission to use this logo.
Alderac Entertainment Group (AEG; Web site here and Wiki entry here) published the entirety of the Oriental Adventures line save for Oriental Adventures proper that was published by Wizards of the Coast.
These books largely concern in and around Rokugan, the setting that's used for AEG's Legend of the Five Rings properties. Some of these books go so far as to include—in addition to Dungeons & Dragons, Third Edition rules—rules for the same things for the second edition of the Legend of the Five Rings role-playing game. (Also see this question. Also omitted from this list is other Legend of the Five Rings, Second Edition material—not my thing.) The prospective reader should take note: These books are not, for example, generic resources for this setting nor do they expand on other Oriental Adventures campaign settings, like Mahasarpa.
Also—and holy crap!—, look at that publishing schedule! That's a new 128-page sourcebook almost every other month! During the d20 boom, too many books were published too quickly and—almost inevitably—quality suffered. These books are no exception, and it may be to your benefit to show a little grammatical forgiveness as you go. These folks' deadlines were tight.
1 Bloodspeakers is an unusual case. Copyright information concludes with this: "Bloodspeakers in produces [sic] by Paradigm Concepts, Inc. under license from AEG." However, the copyright information begins with this: Legend of the Five Rings is produced under license from Wizards of the Coast…." No further AEG material was (co-?)published for the Oriental Adventures line by Paradigm afterward, so there's nothing to compare it to. Thus I've never been clear if Bloodspeakers were officially an "official" product or not. I mean, at this point, who cares, right? The 'Speakers's got some crazy in it, but unless you're intent on breaking the game with its modified Taint rules, there's no more going against it that isn't true of the entire line.