Did you know that you can test your sites with different browsers with only one appliance called BrowserBox?
If you don't want to install various web browsers to your system just to test your developed sites, then I think you have
to test this appliance.
I haven't yet tested this appliance but if you feel you want to test it, common and let's try it together.
There are some sites like browsershot and browseriew that allows users to do that. Free users are limited to number of operating system and browsers but paid users get more options. I didnt tested this appliance either. As i'm rarely concentrating on opera so i'll be using firefox addon or chrome add-on if possible. Thanks for the link though.
For now I just test using IE-tab for firefox, it's stable enough however you can't enter an address and press return otherwise it just reverts back to a firefox tab, refreshing and links etc. still work though.I'll have a look at browserbox and let you know what I think, I've come across loads of things like this before but they never render a page EXACTLY how the selected browser would which just makes them useless if you are working on cross-browser compatible websites in detail. browserbox looks promising though.
I've tried installing this appliance on my VirtualBox. So far, I can't manage to use other browser and I can't manage to install Safari and IE6 on it.
Here's how it looks.