PDFs stink. It's not a Web page (see "Have a link"). It's hard to copy and paste out of. It doesn't show up in browsers half the time. The Web is made of HTML.
Streams stink. Make your video and audio downloadable. You never know when the person who's about to send your file is on the end of a flaky connection through which your stream cannot pass. And this should go without saying, but here it is: don't use DRM. DRM stops people from seeing files -- that's what it's for. If it can't be seen, it can't be blogged.
Put your URL on your images. If you've got cool photos or other images up on your site, stick your URL in unobtrusive type at the bottom of it. That way, when a blogger find the image on some Russian site that doesn't ever link to the origin of its content, she can type the URL into the location bar and find it for herself. (This goes for videos, too -- and the ID3 tags on MP3s)
Linking policies are ridiculous. There is no legal right to control who gets to link your Website (no more than you have the right to control who gets to hand out driving directions to your office). The lawyer who advised you to put up a "linking policy" describing the "terms and conditions" under which the world is allowed to link to your site is an idiot who owes you your money back. Standing on your lawn, shaking your fist at the airplane flying overhead and shouting "Get out of my sky" makes you look like a dork -- so does threatening text about linking to you. At best, you'll make bloggers snort derisively and then go link to someone else.
Don't worry about "bandwidth stealing." There's an enormous fooforaw among site operators about people who "hotlink" to images -- linking directly to images on an external site, rather than to the page the image came from. Dear site operators: Here's a quarter, go buy a terabyte from Amazon S3 and stop complaining. Back in the paleolithic era, inlining could add up to real money. If your hosting company is charging you enough for bandwidth in 2008 that you're still worrying about it, you need a new host. With your URL in your images (see above), every one of those inlining events is just a way of directing traffic back to your site. An inlined image is LOTS cheaper than a Google Ad, and far more targeted. (The same goes for handwringing about "framing" -- including an external site inside a frame on a site, rather than just linking to it.)
Offer high-res images. Whether it's a produt short or something from the news, it's nice to be able to work from a large image so that a blogger can play art-director and select part of the image to snip out and put in a post.