I know that the Assassin's guild has been confirmed or at least Todd Howard used it as an example of the Radiant AI stuff.

I was wondering, are there any others that I may have missed?

No guilds were confirmed. I don't recall a mention of an Assassin's Guild. All I recall is mention of an assassination quest, but that doesn't mean it's related to a guild.

No, you misunderstood it: NPC's may give you assassination's side quests. While DB or some other Assassin Guild will probably be there, it wasn't confirmed yet.

Fighter's Guild, Mage's Guild, and Thieves Guild are almost certainties.
Dark Brotherhood is also quite likely (the assassin guild), or maybe some sort of local, Nord variety.
An Arena would be likely, considering how Nords like violence, if you count that as a Guild.

However none of these have been confirmed.

Touche

Well they confirmed you can kill people..I hope

It is not likely that there will be any Mage's Guild.

Two other mage factions, the College of Whispers and Synod, have taken their place in Cyrodiil, as of the time of The Infernal City (50 years after Oblivion).

Perhaps one of these groups, or some new mage factions will make an appearance in Skyrim.

house Talvani or whatever they called them

that would be nice

also clans would be cool.

Where is all this 4th era / post oblivion elder scrolls lore?

Novel "The Infernal City"

It's in The Infernal City.