You can learn Photoshop very easily from Youtube.com. There have lot's of and latest Photoshop technique. You can learn many more things for there.
I took graphic design in college, but 2 years before that, I studied photoshop by myself without any tutorials. I gave myself a pretty good headstart. Just by exploring the software itself, you can learn a LOT.
At first install a Photoshop software in your computer, and try on your own way. YouTube also provide a lot of video have good instruction of photoshop working, you can watch these video. Those will be greatly helpful for you.
I learned by using online tutorials, mostly at good-tutorials.com. I would just look for stuff I liked and then try to do it myself. I learned a lot this way. I'm not as fond of video tutorials. I find it annoying to have to stop the video to do each step and then if you missed something or don't understand exactly, having to rewind it back. Text tutorials worked best for me.
I suggest you to first play with it. Just doodle on canvas with different tools and options. Use help search in google for particular tools. Once you familiar with the basics then go to the tutorial sites. There are many. If you learn by yourself you will discover lots of magics inside. You use youtube as other friends suggested here, its great helping videos. Feel free to ask this helpful community on dp. You can pm me whenever you need any help.
You can find more details of Photoshop tutorial on following links adobeknowhow.com/courselanding/beginners-adobe-photoshop mashable.com/2010/08/12/12-beginner-tutorials-for-getting-started-with-photoshop/
1 video tutorials on youtube 2 when you will know interface start "to copy" awesome works of another designers. try to find inspiration here: dribbble.com