According to my PHB, there are also: Shadow, Ki, and Elemental.
Ki has been dropped - proscribed, quashed, condemned for being too ethnic - and the one Ki class, the Monk, folded into the Psionic source. Shadow was given short thrift in the Heroes of Shadow book - only two Shadow classes, only one of them new, aside from that, it's just an excuse to give Mages more schools and Warpriests another Domain. Elemental has yet to be developed, but is supposedly queued up.
So the extant Sources that actually have classes to their name are:
Martial
Divine
Arcane
Primal
Psionic
Shadow
Those Sources that have the complete quadfecta - that cover all 4 /roles/ are:
Divine
Arcane
Primal
Psionic
There was a little controversy over whether each source should cover all 4 roles. It was a tad comical, really. When PH1 hit, there were 3 sources, one covered 3 roles, the other 2, 2 each. People asked, "hey, what about a Martial Controller?" WotC responded "we're not going to just do 'grid-filling.'" They then proceded to fill the Divine and Arcane grids, and then introduce Primal and Psionics with their grids, likewise, filled. In doing so, they added classes that had precious little archetypal support - the Avenger (there was already an Avenging Paladin), Invoker (different from the cleric on a technicality), Ardent, Warden, Battlemind, & Shaman - with Monk and Barbarian shoe-horned in to Sources to round them out. Bizzarre. Then, after all that disembling, they introduced a martial/primal controller that overlapped both the Ranger and Seeker. WTH?
IMHO, each Source should cover all 4 roles, for one very good reason: So that a player can take a general concept he likes, and adapt it to fill a role that fits the party; so that everyone gets to play more or less the character they want. If the only Ki class were the Monk (a striker), and everyone wanted to play one, you'd have an imbalanced party. But if there were a Monk (striker), Teacher (leader), Master (controller), and Lord (defender), everyone could play something close to what they wanted without having a lopsided party or stepping on eachother's toes. (I know Ki is dead, it's just a hypothetical example).
Source also plays a big part in the flavor of a character. Martial hones skills, body, & mind to mastery, Arcane cast occult spells, Divine revere and are empowered by the Gods, Primal call up on the forces of untamed Nature. A martial power is already completely different from an arcane power: One will almost always involve a weapon if it's an attack, the other an implement; one might use a wide variety of damage keywords, another consistently untyped damage; and so forth. Those are pretty decent ways to evoke differences. But, /also/ using powers to paint differences among classes gets redundant, fighters and warlords both use a lot of melee weapon attacks, including some that end up quite similar. Sources would feel more meaningful - and, classes would be easier to design and builds easier to add - if powers were grouped under them, and classes differentiated by their features, including role-support in those features.
Finally, as far as mixing sources in a single character, it's fine, and certainly called for - but can be done by Multi-Classing, or Hybriding, or perhaps even by choice of Theme and background. With options like that, you can have /any/ combination of sources you like, a much more efficient aproach than doing such combinations one special class at a time.