Hi,, I'm new to weblogs and would like to know if it's OK to just use any image/logo on the web for my blog. To clarify, I don't mean hotlinking here but what if I just I take some image and save/post it in my own image host provider and use that image in my weblog... Is this safe? how it goes nowadays??

It's courteous to link to the original source to give them credit. Most people don't mind image use as long as you are providing them with a link to their website. Look for copyrights or explicit restrictions on the site beforehand to prevent obvious legal problems. Still, the owner may end up asking you to take it down. Another way to get images legally is through stock image providers. Here's a list of 100 free sources that should keep you busy:

Yes, it's legal because your not advertising it to be sold. But, to make sure just credit the picture from where you found it.