Of course, you can have an (I think) unlimited amount of tables in a database. The hardware in the computer will probably limit you before mysql does
On a side note: I only use one database per site I make. And I always give the tables a prefix like "forum_users", "forum_posts", "forum_threads", "blog_posts", "blog_comments" and so on. Try to organize your tables something like that and you won't get lost in PhpMyAdmin