How can I embed Flash content into Gmail? I want to be able to send New Years flash greeting cards and other such things.
Unfortunately, you can't actually do this. Even if you could, most email clients wouldn't display the Flash content, so your recipients wouldn't see it.
If you have a downloaded Flash file, your best bet is to click the "Attach a File" link above the message body when writing an email. Attach the SWF (Flash) file to the email and recipients can click it to view it.
You can also add a link to the page containing the Flash content to your email. Just click the "Link" button when writing an email or copy and paste the address of the website into the email.