One of my favorite ways to add some pop to a photo is to use the Soft Light layer mode in Photoshop. I think I first learned this technique over at The Pioneer Woman, but I have a horrible memory so I could be wrong.
Anyways. This is a really simple technique that can really brighten up a photo. Let's start with this picture I took last weekend of a lady bug.
Now, in the layers palette (below) right click the background layer and hit "duplicate layer". You can name the new layer whatever you want, or you can be original like me and leave it as "background copy". Next, go to the little drop down menu and change it from "normal" to "soft light" like I did below. This time I left the opacity at 100%, but you can play around with it until you like what you see.
Then you can go to >Layers>Flatten Image to combine the two layers. I usually do an unsharp mask filter at this point to get rid of the blur and make it sharper (sounds funny, unsharp to make it sharp). Now we have a new photo with brighter colors that gets rid of what I like to call the "gray film" that is on most digital camera photos.
Here you can see them side by side. Notice, no gray film.
I did the same thing with the bee photo from yesterday, see?
Now, there are definitely times when you shouldn't use this technique. In general, soft light will brighten up the highlights and darken the shadows. So if you have an image with shadows, and you want to preserve the details in the shadows, then I wouldn't use soft light. I found it also doesn't work well if you have shadows on a face in a portrait shot, it just gives too much contrast.
You may also notice that there are other layer modes to choose from, hard light, screen, vivid light etc. I find that playing around with the different modes can give some really cool effects on certain photos.
Don't just take my word for it (I'm definitely not an expert), go play around with it and see what you can do.