I’ve been using the Mail app on the mac often these days, and I wanted a way to imbed images for a custom signature I had in mind, but adding a signature through the normal way does not allow much functionality other than the normal font, color, and some minor text effects.
Luckly, through some digging I was able to find this blog. Follow the necessary steps and you can have images in your signature as well. Along with any CSS you want to add.
http://allforces.com/2006/04/14/css-signatures/
Enjoy!
If you’re running leopard on your mac, this little trick might come in handy while using Share Screen to connect to a remote computer.
Copy (apple+c) the item you’d like and then from the Share Screen menu select Edit > Send Clipboard. Then in Share Screen simply paste (apple+v).

I found it handy if you just want to copy text between both computers, but any thing you can send to the Clipboard should work.
Barton Springs Software is now offering a Flickr client for Mac OS X. From first glance, this looks great to help manage photos, contacts, etc. You can download a free demo, and full version for $20. Both basic and pro accounts are compatible with the software.
Check out their web page for more info.