You can change the time increments shown in your Outlook calendar to allow for smaller more detailed calendar entries. This will work in Outlook 2003, Outlook 2007, and Outlook 2010.
You may not have all the calendars showing on your iPhone and in Outlook. This could prevent you from seeing events that you create in Outlook on your iPhone, or vice versa. It is easily remedied. You will want to make sure you are displaying all the calendars on your iPhone as well as in Outlook. This process is shown on iPhone, but works the same on iPad.