What are all the factions I can join, and what are their restrictions?

Question

I have started a new game. In previous playthroughs, I normally just joined the Fighters Guild, but this time I'm going to try and complete as many quests as I can, and that includes all factional quests.

In a previous playthrough, after I got so far through the Fighters Guild, I went to join the Thieves Guild but was rejected. In another playthrough, where I was in the Thieves Guild, I was rejected from joining the Mages Guild.
In each playthough I had at least 2 skills which would work with each guild which I was building (a basic set of skills I always select).

• Thieves Guild — Acrobatics, Athletics, Security
• Mages Guild — Alchemy, Restoration

Since I want to try and complete every quest for every faction, and given that I was rejected from guilds in previous playthroughs, I am wondering what all the factions are which I can join, and which restrictions may stop me getting in later in the game, or which quests I'd end up doing which could see me kicked out.

This is a list of factions I am aware of:

• Blades
• Fighter Guild
• Mages Guild
• Thieves Guild
• Morag Tong
• Imperial Legion
• Imperial Cult

Answer 1

This is a complete list of the joinable factions in Morrowind. A quick Google search of any one of them should be able to help you find any notes regarding how you join them. Don't forget: Joining certain factions closes you off to other ones, and you cannot advance in certain factions beyond a certain point if you've already done a certain amount in another faction. For example, if you've killed the heads of the Thieves Guild for the Fighter's Guild questline, you obviously cannot advance in the Thieves Guild without console commands. There are other NPC factions, and not all these factions will appear in your faction list, but they are all player factions nonetheless.

House Hlaalu

House Redoran

House Telvanni

Blades (Necessary, joined during the main quest)

East Empire Trading Company (Comes with Bloodmoon Expansion)

Fighters Guild

Imperial Cult

Imperial Legion

Mages Guild

Thieves Guild

Ashlander Tribes (Only technically one faction, but becoming friendly with the Ahemmusa, Erabenimsun, Zainabs, and Urshilaku puts you on friendly terms with all the others. You automatically do this during the Trials in the main quest)

Morag Tong (don't listen to the comments that say you cannot join. This is FALSE. You can join by going to their Vivec headquarters in the Arena Canton. In the storage area underneath the arena, talk to Eno Hlaalu. He can initiate you with a quest. This is the only way to join, you cannot join in their guild halls)

Tribunal Temple

Aundae Clan

Berne Clan

Quarra Clan (These are vampire clans. You can only join ONE of them. It will not appear in your faction list, but it will affect the bonuses you receive as a vampire, and what vampire quests are available to you.)

Hope this helped! :D

UPDATE

As for the latter part of your question, if you go to this page on the wiki:

http://www.uesp.net/wiki/Morrowind:Factions

There is a chart down at the bottom that shows the prospective relationships between the guilds, including NPC factions. What that means is that it shows the likelihood to like and/or attack you on sight based on your belonging factions.