I am using a Raspberry Pi in an industrial area as a data-logger and had to deal with SD-Card wear so that I decided to use SLC-SD-Cards with higher quality. 

To keep costs for those card types low, I am currently trying to figure out how to shrink down the Raspbian Image to a very small size so that it will fit onto a 1GB (or 2GB in the bad case) SD-Card!

I have purged a lot of packages - including X11 - but still have a disk usage of remaining 1,8GB. Less would be better!

What I need for running my application is:

 - Python 2.7.x
 - lighttpd-Web-Server 
 - PHP 
 - RRD-Tool 
 - SPI-Library
 - Bonjour/Zeroconf

I was also thinking of using a different system - other than Debian, like buildroot but I have absolutely no clue if this is necessary and what to do to install buildroot linux.

Additionally I could ask this the other way round: When using the official 'Lite' version of the Raspbian System it comes with a size of approx. 1.3GB which is - like mentioned in the comments below - a bit closer to my 1GB. But where do that 1.3 GB come from when all I want to do is put up a very small websever + python script and a database of less than 5MB !?