[PH-LKK]

Just to add to Celtic's fine summary: SMAC is gone, as is StarJets (both went belly up a while back now). You may still find these brands advertised by various retailers, but it is always older stock (plenty of them are still floating around). SMAC had its very own DC-9 toolings, but otherwise borrowed toolings owned by AeroClassics (for its 737 and 747 releases). Some of StarJets toolings have been bought up by Herpa, but are otherwise used by 5Star (a brand that issues black market models).

There are a couple of additional things you may want to keep in mind: Many "brands" use the same toolings, and are manufactured at the same factories, but nevertheless originate from different "companies". Some of it above board (like Gemini Jets issuing models using AeroClassics toolings), and some of it deep under the table (like Pan Am releases using AeroClassics toolings). A quick run down:

1/400
AeroClassics toolings are used by AeroJets (commissions), Aurora400 (commissions), British & Irish Classics (fully licensed), EuroClassics (fully licensed), Gemini Jets (fully licensed), Green Box (black market), Pan Am Model Co. (black market), Phoenix (black market), and Sovereign (gray market).
Gemini Jets toolings are used by 737Club (defunct), AeroJets (commissions), Aurora400 (commissions), BiggestBird (black market), Black Box (black market), DreamJets (black market), Golden Falcon (black market), Phoenix (black market), RetroJets (black market), SkyJets400 (fully licensed), Sovereign (gray market), and White Box (black market).
BigBird400 (defunct) toolings are used by AeroClassics, SMAC, and now Inflight400.
Seattle Model Aircraft Company ("SMAC") (defunct) toolings are used by Sovereign (gray market).
Dragon Wings toolings are used by BigShooter (black market), DoDo Diecast (black market), Flying Colors (black market), Jet-X (fully licensed), SuperWings (black market), TwinStar (black market), and Nintendo (fully licensed).
In addition, some Tucano (defunct) toolings, after refitting, are now used by Gemini Jets, Sovereign (gray market), and Phoenix (black market).

1/500
BigBird (defunct) toolings are used by Herpa and Inflight500.
StarJets (defunct) toolings are used by Herpa and 5Star (black market).

Some folks, you will notice, use toolings from more than one source, such as Sovereign (using AeroClassics, Gemini Jets, SMAC and Tucano toolings, depending on the airframe). Others borrow toolings only occassionally for specific air frames (Gemini Jets uses the AeroClassics L-1049 and Convair toolings, and uses a TU-154 tooling which was adapted from the Tucano tooling after Tucano self destructed, but uses its own toolings for all the rest). And finally some are exclusive to a particular source: DoDo Diecast only uses Dragon toolings. Generally, the quality of a particular model will correspond to the quality of the tooling's owner (thus a Gemini Jets L-1049 has the same level of quality as an AeroClassics L-1049, and a BlackBox 737 has the same level of quality as a Gemini Jets 737). You also need to be careful with some of these, as the "BigBird400" name (sometimes just "Your Craftsmen") is now being used by a company putting out models using a tooling *not* used by the original BigBird entity (the toolings have gone to Inflight400, and are occassionally used by AeroClassics). A black market company calling itself "Blue Box" (not connected with the BlueBox toy and model manufacturer) has started using the BigBird name now that the original BigBird is defunct.

1/400 tooling sources to avoid, IMHO, in no particular order: BlueBox (the black market "brand"), C&C, Tucano.
1/400 tooling sources to seek, IMHO, in order: BigBird400 (prior to mid-2006), AeroClassics, Jet-X (only DC-9 toolings are home grown at this point), Gemini Jets, and Herpa (particularly the new PBY tooling).

It's all rather dizzying. If you have questions about a specific model, feel free to ask.