Link to create new node with taxonomy term from url already selected?
Yes, you need to download and enable the Prepopulate module.

The syntax you use to prepopulate taxonomy terms with D7 is (AFAIK) not documented anywhere and the syntax it is also radically different from the syntax used in D6 that is demoed in a number of screencasts of the Preopulate module.  In D7 taxonomy terms are fields.  If you read the source code, you'll find that you prepopulate taxonomy terms as would prepopulate other field.

I.e. if your taxonomy term field is field_tags and you want to prepopulate with the term "myterm", you use the following syntax (with clean URLs):
/node/add/article?edit[field_tags][und]=myterm.