Anywho, for anyone interested in getting into Mobile Suit Gundam:
This is the vast majority of current Gundam anime releases, in their respective time-lines. It may look confusing, but think of it this way:
Universal Century is the core series. All other series and shows span off from "Mobile Suit Gundam Series 1", which is the initial entry into the Universal Century setting (UC). If you want to get in depth on the show, then the original Mobile Suit Gundam (MSG) run is the place to start and can be viewed in one of two ways. There's the original series that was aired on TV, which has just seen a Western Blu-Ray release, alongside its much older DVD version. The second way is the Mobile Suit Gundam Trilogy. The Trilogy, although it may sound like an unrelated item, is basically the entirety of the initial series, compressed down effectively into 3 films. This makes for a much swifter and less saggy watch, with the vast majority of core story elements and episodes present and accounted for.
There is a 3rd, newer option as well, in the form of the MSG: Origin OAV series that is currently releasing (Part 3 of 4 coming soon if I remember correctly). However, this is both a retelling and also a slight retcon from the original series. It's set at the same time (UC-0079), but tells story aspects from an antagonist's point of view as well as looking more in-depth at behind the scenes type moments, which only get glanced over in the main series. It's a solid entry and a good way to become acquainted with the Gundam universe as a whole, but it does change a number of minor elements, so keep that in mind.
If you want the core story that Gundam was originally centred around, the following anime should be watched, preferably in this order:
Mobile Suit Gundam (Original series or movie trilogy)
Mobile Suit Gundam Z
Mobile Suit Gundam ZZ
Mobile Suit Gundam Char's Counterattack
Mobile Suit Gundam Unicorn
This is quite a lot to watch, but is the entire core of the main story that started it all. The only exception in that group, I would suggest is Unicorn. It was released only recently and is quite fan-servicey in many ways, but has literally some of the best mecha animation and art ever. It closes out the series effectively and is a great end-piece, though it may not be as satisfying as the original series was.
What about all the other shows listed on the UC timeline? The majority of these are miniature expansions of story-threads, or battles, that canonically slot into the UC timeline's overarching storyline. They are not essential watches, but a lot of them are very good. 0080: War In The Pocket and MSG 08th MS Team often come up as some of the highest rated MSG shows ever.
So then, what about the other 'Centuries'/timelines dotted around? Essentially, these are all spin-off series, with no baring on the UC timeline. They are all separate, existing in their own personal bubbles and can be watched with no prior UC knowledge. Most of them are what you get when people not related to the creation of the UC timeline want to create Gundam based stories, without being confined by the existing back-history. The results are widely varied and very mixed. One of the best shows from this bunch is Mobile Suit Gundam 00 and its sequel movie - Mobile Suit Gundam 00: Awakening Of The Trailblazer. Gundam Wing and SEED are popular in a lot of circles too.
OK, so what exactly is Gundam? At its heart, Gundam is a war-story. It tells of an epic conflict that spans 20 years, with varied political influences, personal conflicts and large scale battles taking place across its span. The cast is huge and changes over time, as different stories focus on different conflicts and interactions. New friends and enemies are made, people die and grow across the shows. The earlier segments of the show were fairly black and white with how the conflicts were viewed, becoming far more grey and often quite dark in later shows.
The titular Gundam mobile suits are a fairly major part of the initial shows, being essentially cutting-edge, advanced technological weapons that can decide battles almost singularly, until they become more common place. We join the story at the point where they are only just starting to show up with any regularity and they are seen as wonder-weapons by most. The introduction of new Gundam units is almost always a pivotal moment in later series, whether it sways the tides of war, or simply gets a cheer from the fans.
And finally, what is this Correct Century 'CC' thing? The corrected or 'Correct Century' is a bit of an oddity. It essentially takes the Universal Century, Future Century, After Colony and After War centuries and creates a single time-line out of it all, using all these existing timelines to forge a new future, where all events from all those listed centuries have occurred. From this menagerie of times and stories, we get Turn A Gundam. Turn A is a surprisingly good series in itself, although its animation is quite weak compared to a lot of the more contemporary shows, its story, art and music are all pretty much fantastic and it's well worth watching. Due to its futuristic setting (set 2100 years after the original series), it has a lot of freedom in what it shows and how it handles itself, not having to integrate itself with any of the UC's main storylines.