Weblogs

Hi,

I want to write an application in Web for writing letters automatically.
This letters are produced by selecting some objects and putting them
together. For example the template, layout , logo, ...for each letter.
The main text will fill by user and insert in its place in the template.

The whole idea is very similar to what the weblogs do. However, I don't
know what tools and software I need, and what 's the best way of writing
this application.

Any feedback or hints of you is most welcome and I appreciate.

Regards,
Bita.