In Gmail, hover over a contact in the Google Chat section of your left hand menu to open up a contact box and quickly send them an email.
You usually have close contacts or people you regularly talk with in your Google Voice or Chat section of the left hand menu. Try using the menu to send quick emails to your contacts. Hover over a name to open a details box where you can choose to send an email to that person.
The details box also has a More button, under which you can choose to see Recent Conversations or open contact details for that person - if you have a webcam it's also where you can start a video conversation.
If the contact is offline, it's even easier to send an email - just click on the persons name.