While teaching a class this week, several questions came up re: saving sites as templates so I thought I'd post the answers in case others have the same questions.
Q: Why is the "save site as template option not available for some sites?
A: The "save site as template" option is not available for publishing sites. Also, some have found that they can navigate to the savetempl.aspx page directly and save the site, but proceed with caution here because I don't believe that this is a supported scenario should something go wrong. You might also want to check this KB out.
Another option you have is to use the stsadm -o import / export operation. Check out the capabilities and limitations here.
Q: Is there a way to save a content type as a template?
A: No, not directly. Save the site as a template. If someone has a better approach let me know.
Q: Is the site template size still limited to 10MB in WSS v3?
A: No. Use the stsadm command to increase the size:
stsadm -o setproperty -pn max-template-document-size -pv 50000000
(where max-template-document-size is in Bytes)
Q: Why aren't Web part settings maintained when saved as part of the "save site as a template"?
A: Known issue. Check out the KB article:
Changes that you make to the "List View" Web Part are not retained after you save the site as a template in Windows SharePoint Services 3.0
Unfortunately, the KB article doesn't talk about how to fix. I have used an involved process of editing the manifest file inside the .stp file and have had some success but I'm not going to post that process here because I have not thoroughly tested it, especially in a production environment. I have heard some other folks have used the data view Web part but I have not tried this myself.