Basic SQL server setup questions...

I'm new to using SQL server and have a few setup questions.
I'm setting up a database for the company I work for. Should I setup a different database for each division in our company (e.g. accounting, project management, estimating, etc.), or should I use just one database? It seems like it would be easier to use one database so I only have to use one connection, but is this ideal? I want all the info from the different divisions to be used together, but at this point I'm confused as to how to connect different databases together, if I were to go this way.

Thanks for any input or ideas!I create seperate databases based on the app function - not the company division.
many times you'll get people from different functional areas all using the same apps...

anyways, you can get to all the data in a single db with a single connection if its all on the same server. you just need to qualify the table names in your queries with a prefix of the database name.

i.e.

AccountingDB.dbo.table.column

since this is a pain to type, in one of our dbs that shared a user table with an existing db, we created a view that pulled all users from the other db. now our new database has a local view that we can treat like a user table...one connection can pull data from 2 (or more) databases :-)