There are many that you can use. if you want to use one online and which requires no logins or anything, just go to pixlr.com and choose which ever basic or advanced version. the advanced version is like Photoshop and will do more than you need. I use it on my blog for artwork. Lots of people say it is the best free application out there. There are other versions, but I use this.
Also check out and maybe download PhotoFiltre 7, as this is free to use and easy to fix, crop photos and re-jog colors and fix up photos.
I do use Photoshop and it is awesome. But I found a great package in Xara Designer Pro and it is stunning and if you needed to buy one that did everything, then it is great value for money, Xara is easy and best to use. I use it on my blog a lot. Text handling and shadows and graphics are just so simple on it.
You have lots of choices.