The answers (I think there are a few) depend on your immediate goals and budget. After 5 years plus of online marketing, here's how I'd stack the list:
1. Pay Per Click - very effective given time and good copywriting
2. Search Engines - if you have good in-house SEO, cost-effective and worth the effort
3. Networks (Fastclick, etc.) - relatively low-cost approach to banner ads
4. Banner Ads - good if you can afford to test, test, test & find the right place to show them
5. Press Releases/Newsletters - good for "newsworthy" items, but not so good for general, everyday changes/updates to your site
6. Forums - you are at the mercy of those who post and their personal views
7. Blogs - again, find the right one(s) and it's worthwhile
8. E-mail - very tricky to do correctly now - use a reputable e-mail company and make, don't buy, lists
9. Content Partnerships - if you have the ability, this is a great way to get your content and name spread about
10. Affiliates - had to put this here - I personally don't like the idea of trusting others to handle our marketing - an agency, maybe, Johnny Lunchbox who just started their first website - ah, no... (BUT, this can work if YOU are willing to vet each possible affiliate yourself & provided they actually have traffic and skills)
...Podcasting is right up there with Internet Radio, IMO - please note it's not on my list - it might prove worthwhile for some things, but the bottom line is I will always put money into things which can result in traffic NOW - not something which relies on a person to remember me later, when they're at their computer. This is why newsprint, magazine and TV don't make the list (not to mention the stupid amounts of money they consume) - if it can't be tracked, it doesn't exist.
Now here is some of why my list looks the way it does:
1 - we have a large marketing budget ($100,000+ per month), so buying traffic is pretty straight forward
2 - our sites contain tens of thousands of pages of content (actual articles, etc. from the past 10 years of being online) plus, given our topic (sports), it's easy to dynamically generate data on, say, team stats...hence the large number of pages
3 - usability is our # 1 concern, so things like (my personal fav) SEO, take 2nd seat to that.
If you were starting out with a limited budget, my list above would, and should, look markedly different.
Sorry for rambling on so much, but, since this is one of my first posts, I wanted to (hopefully) at least try to sound intelligent.

Comments above are based on actual experience I've had with those areas, not conjecture.