Belenus
The Celtic sun god, observed in Gaul, Cisalpine Gaul, and Celtic areas of Austria, Britain and Spain. Variation of Apollo. BeleniX, an open-source Solaris distro (now defunct), is named in his honor.
Freyr
The Norse Pagan sun god, also widely renowned for being a phallic fertility god. It's really, really hard to find depictions of him that don't involve a dick, dildo, or other suggestive depictions. Even here, you've doubtless noticed that big ol' sheathed sword he's lugging around. Oh, that's his wild boar, an indispensable sidekick.
Horus
The ancient Egyptian god, great-daddy of all gods and more like the god of the sky - the sun was his right eye and the moon was his left. Since sky = flight = birds in Egyptian parlance, he's usually depicted as a man with a falcon's head. The symbol of "the Eye of Horus" is still today the most iconic symbol of Egyptian mythology. However, you could just as easily nominate Aten or Ra as the Egyptian sun god - they were all intertwined, Egyptian theology being a very convoluted subject.
Moloch
A bit scarier than your average sun god, Moloch was worshiped by
Canaanites, Phoenician and the general neighborhood in North Africa. He's got something of a bad-ass reputation, even a Satanic one, because he's one of the few gods expressly forbidden by name in the Christian Bible. Leviticus names worship of Moloch as yet another stoning offense not once, but twice. Jeremiah again mentions him as the sub-fire-god under Ba'al. In fact, wherever the Bible speaks out against idolatry, it's pretty much talking about this guy. The scary part is, his worshipers sacrificed human children to him.
Sol
Well, now, we're probably on familiar ground here, right? Yes, the Roman sun god is the very same from which we draw all root words referencing the sun in English and most Western culture. Sol was the sun, Luna (another Roman hand-me-down name to English) was the moon, and Janus was related, being the two-faced god of transitions, beginnings, and endings, and hence invoked with the rise and set of the sun and moon. And also hence, we name the first month of the year January in Janus' honor, because that's when the year turns over.
Surya
The Hindu sun god, also the head of all sky gods and again, associated with general fertility, nature-worship, fire, etc. Still very much actively observed in Hindu circles today; he has temples with services attended at dawn and everything.
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Solar deities are simply a dime a dozen, the complete Wiki on them here.
Here's a thought to all this: Isn't it an interesting coincidence that every part of the world founded its own religion based on the brightest object in the sky? Certainly, if one is compelled to identify the natural object most likely to be the embodiment of a deity, the sun fits the bill. But what superstitious monkey-minds we have! When we consider the vast array of sun gods and the remarkable similarities in ideas about them, it tells us much, much more about how the human mind works than we'd care to admit.
And before you get too smug thinking that the God of Jews, Muslims, and Christians is any different, and hence (if you observe one of these faiths) not at all based on silly star-worship, take a gander at "Jesus Christ in comparative mythology" and ask yourself why "Sunday" is observed as "the Lord's day" and Christ's birthday is celebrated at the winter solstice.
But here's a far more complete article on sun worship and its place at the roots of modern religion, courtesy of The Review of Religions.
Not so smug now, are you?
