Calendar Web Part Standard Edition Features:

• Aggregate events from multiple SharePoint lists, from any site, in one Calendar view     
• Supports any SharePoint list type (not only Calendar list) in any location     
• On-the-Fly events - dragging, resizing, editing     
• Adding and deleting events with a single click     
• AJAX support     
• Color customization for source lists events (Background color, Text color)     
• Event coloring according to event column values     
• ArtfulBits Category Column integration     
• User permissions for Calendar sources     
• Customizable extended tooltips
• Hour split count (for more precision event displaying)    
• Customizable time display format for calendar events (None, Start Time, Start & End Time)    
• Quick date navigation (using cross-browser Date & Time picker)     
• Ability to switch between "Work Week" and "Full Week" on calendar's weekly view    
• Ability to expand events by default on calendar's monthly view     
• List view toolbar     
• Cross-browser support (IE6+, Mozilla Firefox, Google Chrome, Safari)     
• SharePoint standard themes support 

Calendar Web Part Professional Edition Features – all features included in the Standard Edition plus the following:

• Bind to SQL     
• Calendar sources filtering by query parameters     
• Programmatic Calendar source filtering by client-side scripts