Here's a list of 10 top links that I've found useful in the setup of my business and creation of my website:
1) UK Business Forums An excellent forum that covers most things that you need to know for running your own business. Lots of knowledgable people on who can answer your questions.
2) WebCEO All round SEO program that lets you research keywords, optimize your site, submit/check search engine links, anlayze traffic and more. It does cost about £6 a month for the basic but I've found it worth the money. The traffic analysis gives you the search terms used to get to your site and also lets you keep track of any file downloads from your site.
3) Adbrite When you get banned from Google Adsense(I lasted just one week on it!) try Adbrite as an alternative way of monetizing your website or advertising your own.
4) AdsFlip A nice free way of advertising your site. You earn credits to advertise on the network by displaying other people's adverts on your site. Lets you advertise with banners or text only adverts.
5) Google Adwords It's the easiest way of getting your site on the first page of Google results and with Google controlling nearly three quarters of web traffic it's a must for a business especially in the early days.
6) Google Analytics free webpage traffic analysis.
7) Google Webmaster Tools Submit your sitemap and find out how your site is doing on Google.
8) Xinu Returns SEO site tool. Lets you quickly run a report showing how well your site is doing in search engines and social bookmark sites.
9) Yahoo Answers Answer some questions relating to your business area and in the source box add your site. Simple way of getting traffic from a major site.
10) Business Link Government run site that gives you all the information and links to forms etc that you need to set up your own business.