And now... the Not-so-Free Plug ins.
Before I begin on this section, All of these where given to me through a family member or friend, which is how I came about them. I will not help anyone find ways of getting them for free, but nearly all of them have a free trial or demo, so you can play with them beforehand. Some of them though are pretty cheap, so it wouldn't hurt you too much, but if you want to find "ways around that" I won't tell if you don't :P
Axion Flare Effects: I can't even begin to describe how wonderful this thing is.... Okay yes, It's a Flare Effect. Yes, I know Photoshop has a built in Flare effect plugin too, but Photoshop's has NOTHING on this thing. Not only can you create custom flares both with and without the lens glare, it comes with several odd effects that I've come to find out are particularly wonderful for other things like water effects, or strange twisting light streaks.
And in that same link... we have "glow n' Sparkle": Glow n' Sparkle can add some nice shiny glows when you just can't. It has two settings for this: glow, and ....well...sparkle, which fills up the color/space you picked in question with sparkles, or just leaves a soft toned glow when a normal "new layer-blur" just can't seem to cut it.
Flaming Pearl's Blade Pro: Not exactly a "must have" for me, but is very useful none the less. You can draw simple things, and it can apply a strange, metalic-y, rustic, texture to them. The most useful of this is for text for that manga cover you've been meaning to redo to make it look cooler, but can also apply to buttons, or maybe just some do-dad design on the side, or a logo.
I've never even heard of some of Flaming Pearl's other plugins but they seem really nice too. They also have a Freebies and goodies page for the rest of us that can't buy stuff X3
Alien Skin's Eye candy pack: I've never used these, but a lot of the features can also be found in that Alien Skin 3 pack, so I know at least that some of it's good. Considering how Alien Skin plug-ins are pricey but very cool, I say at least try it out.