One of my favorite improvements to GMail is the ability to automatically forward anything in your inbox to another email account. I had been concerned about backing up business email sent to my GMail account. Now, I just forward everything to my POP account on my local ISP - from there it is trivial to do a local permanent archive.
Yesterday I configured my Firefox browser to use the clustering "Clusty" search engine for the defualt browser (although it is very fast to do searches also using Google, a9.com, etc.) I left Google as my default search engine for Safari (the browser I use the most).
One thing that makes Clusty so interesting to me is that I have been working (for the last year and a half, although lately because of a full time consulting job I have had to put this development on hold) on version 2 of my KBtextmaster product that uses similar technology: I cluster documents based on what categories I automatically assign to them (for this, I use the Reuter's categories and trained with their excellent 2+ gigabyte tagged news corpus). I also identify people's names, places, etc. and I am planning on using this information to improve clustering also.