Sounds like an ad for software piracy: Get Photoshop for Free.
But you can, to an extent, as Adobe's just launched a free beta of the image editor online called Photoshop Express. I've only piddled about with it but I use the real Photoshop a lot and can see that this is no replacement. However, it's easily the equal of your basic PC photo editing tools or even iPhoto on Macs: you can crop, alter exposure and saturation, fix red-eye, a great many things.
Only, it's online. If you don't have an internet connection, you can't use it. This may not seem a big issue since if you haven't got an internet connection, you aren't reading this.
But I have Sky Broadband: I know what it's like suddenly having no internet.
There's a strong argument that the future of applications is online: Google Docs is at least a fair replacement for Microsoft Office (apparently: I've never used the Google apps), for instance.
I think I sit on the opposite side; I'm willing to be proved wrong but I just feel I've seen this before. Most recently on iPhone: there are now thousands of web-based applications but I find them all too slow. And back in the day, working on computer magazines at Ziff Davis, everybody ran Microsoft Office but they did so across the network: the apps really belonged on the server and a fast connection let everybody work.
Until the server would go down.
Everybody would swear - and that's when I'd know. Because I ran those apps locally, I was always testing/reviewing the next Office release, and carried on working normally.
'Course, there was one time when everybody else in the office went home early because of this and I was left there until I managed to hook my foot around the mains plug...
I have no idea why I wanted to tell you that. But have a look at Photoshop Express, won't you?