Well I would develop a custom application but in your case being you like the design aspect more you can get a free php app for calenders and such. PHP has a lot of free stuff out there.
Server type is an issue, you probably want to use a Linux server if you go with php and if you go with asp or .net apps you want to go with a windows server. You could put either on both types however hosting companies usually set restrictions and don't make that possible. Also if you are going to use a database your going to need to be careful in researching what they actually let you do with your database. Sometimes the database will not let you have the control you need to do what you want.
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