Difference between SPWeb.Groups and SPWeb.SiteGroups

SPWeb has two sharepoint cross-site group collection, SPWeb.Groups and SPWeb.SiteGroups. SPWeb.Groups returns collection of cross-site groups which has some permission on the site. So if you add group from a site without any permission on the site, then this group wont appear in SPWeb.Groups collection, but it will appear in SPWeb.SiteGroups collection.
You can not use SPWeb.Groups.Add method to add new cross-site group, you need to use SPWeb.SiteGroup.Add method for this purpose.

Info from Sridhar

Link a file to a sharepoint webpart

I found this post recently, very good read for those who are struggling with that problem
http://msdn.microsoft.com/en-us/library/dd584169%28office.11%29.aspx

How to make your intranet sharepoint site be live

The easiest way to do make your sharepoint site live would be to use an SLA that will redirect the user to your intranet site when the url you assigned it is hit. (More to come to explain how to achieve this)
For those of you who do not know what an SLA is, follow this link http://blog.sharepoint-recovery.com/2007/09/17/whats-the-service-level-agreement/