The Best Scripts for Gmail

• Gmail Conversation Preview
• After right-clicking a conversation, view the newest message in a bubble.

• GMailSecure
• Always use https://mail.google.com/

• Gmail Signature Float
• Place your signature on top of the newest message so the receiver can see it.

• Gmail attachment reminder v2.2
• Reminds you if you refer to an attachment but you forgot to attach it.

• Gmail + Google Reader
• Integrate RSS feeds in Gmail with a "Feeds" button under "Starred"; list view

• Gmail + Google Reader (Alternative)
• An alternate version of the above script. Personally, I like the above one better, but some may like this better.
  

• Gmail Saved Searches
• Quick searches for complicated queries

• Gmail Macros
  
• Create your own and use additional keyboard shortcuts
  
• Gmail One Click Conversations (formerly Quicker Contacts)
  
• View recent conversations in one click, as well as contact information with a simple mouse-over (like the quick contacts panel)
  

• Gmail Make it Comfortable
  
• Make your GMAIL more comfortable for reading messages. Hide ads, stretch message window for necessary size, and other fixes.

• Google Air Skin
  • A Skin for Gmail and most of Google products

• Gmail Air Skin 2 (with ads-block)
  • A new Gmail Air Skin with ads-block for the new version of Gmai.
• GMailAgenda
• Integrates your Google Calendar in to your GMail account plus some other improvements.

• Gmail Full Width 2
• Removes the advertisment box on the right and the message and reply box occupy the full width available.

• Gmail - Insert HTML Signature - v 2.1.1
• Inserts your HTML signature(s) into a GMail message. Works only with new version of GMail.