Daily calendar activities are a part of almost every elementary classroom I've been in. Here are five great sites for creating calendars. These sites are great for teachers and could also be used by students to create calendars.
Worksheet Works- This site would be great for teachers to create calendars or for older students to create their own weekly planners or homework calendars.
Starfall- Known for great literacy activities, Starfall also has a wonderful calendar area. Teachers could use this calendar as an online alternative to the daily calendar used in many classrooms. The calendars can also be printed out in black and white or as a missing number activity for students to solve.
Printable Calendar Templates-This site is great for creating and downloading editable MicroSoft Word calendars. I have used the templates many times and I have also had students create year long calendars right after New Years.
Jan Brett Calendar Maker- Students will enjoy making a calendar featuring some of the wonderful characters in Jan Brett's books.
Traceable Calendars- Great for students practicing number writing and recognition. Each calendar is pre-made and can be downloaded as a pdf file.