How to add managed property and configure advanced search in SharePoint

Here is very good detail information about how to add managed property from central admin site and how to use same managed property into advanced search page:

http://waelmohamed.wordpress.com/2011/05/31/add-custom-search-properties-in-your-advanced-search-sharepoint-2010/

SharePoint 2010 Search Refinement Panel web part

In SharePoint 2007 - I have used "faceted search" from codeplex http://facetedsearch.codeplex.com/ to grouping search results by different category name, total number of values inside group, etc... BUT SharePoint 2010 provides OOB web part called "search refinement panel" in which we can achieve more or less same type of results and output like faceted search.

For achieving grouping functionalities in SharePoint 2010 search refinement panel web part - we can create managed property from central admin and can customize XML for search refinement web part to display search results by different categories.

Result type, site, author and modified date categories are by default in search refinement panel web part.

Here are some reference links for customizing refinement panel web part in SharePoint 2010:

http://searchingsharepoint.wordpress.com/2011/06/09/customizing-the-refinement-panel-for-sharepoint-2010-search/

http://microsoftsharepointandbeyond.blogspot.com/2011/04/sharepoint-2010-refinement-panel.html

http://vinaybhatia.blogspot.com/2010/11/add-custom-category-to-search.html

http://msdn.microsoft.com/en-us/library/ff625183.aspx

Block specific file types while uploading from SharePoint interface

One easy way:

We can block specific type of files from entering file extension into “Blocked File Types” from the SharePoint Central Admin Site -> Operations-> Security Configuration.

We can select specific web application for blocking or not allowed file types/extension list.
 
Other way:

We can also do programming and modify current Upload.aspx page, we can write simple JavaScript by checking file extension and content type when user is uploading any file and then we can give alert to user if its not valid file type or extension type for uploading into SharePoint.