although I have my doubts that they'll allow it.
As Taran says, the legalities involved in your site's content are serious matters, and you'll need to address them sooner rather than later. The technical issues are fairly straightforward, and we'll be able to help with those, but you must not use copyright protected images without the owners' consent. Grabbing images from other sites is not something you do lightly, and some companies get very touchy about it - many budding web designers have received 'cease and desist' letters from solicitors on this issue. Some site owners are happy to grant a free single publication copyright licence if they think that your site is the kind of place that they would like to see their image displayed. In these circumstances it's normal to put what's called an attribution alongside or below the image - a small line of text saying 'image with kind permission of (photographer or originator's name)" etc., but you must ask.
It's also good Internet etiquette to ask people before linking in to private web sites, and you should never, ever link into an inside page without explicit consent - just the index page. Big organisations like Microsoft or the BBC understand that millions of sites will link to them, so it's not necessary to ask.
Don't use other companies' logos without their consent - Microsoft do not allow any of their product logos to be used unless they have granted permission, and most big companies are the same. Many of them have application forms on their websites, and in those cases you'll often find that they insist on the images being used without any alteration in size, and that they are displayed against specific background colours. Often they'll want to look at your site before they give a decision - it's all about protecting their public image.
It can be a bit of a minefield, and the golden rule is: "when in doubt, don't". Ask first, and you'll be safe. In the past people have broken the rules and got away with it, but nowadays companies are far more agressive about protecting their copyright property, and you flout the system at your peril.