arduino start kit - finished whats next?

I finished the started kit what should i buy next tons of different boards can someone point me to the differences and applications for these boards?

We can't tell you what you should buy next since we don't know what you already have, nor what are your interests, nor your budget. That being said, it's always good to have a range of caps and resistors, a bunch of LEDs, one or two breadboards, lots of jumper cables, various switches and buttons, some hand tools, a multimeter, a soldering iron...

http://arduino.cc/en/main/boards

Do you have a project in mind?

Have a read through the playground page.

Maybe: http://www.cray.com/products/computing/xe-series?tab=overview

Sorry, 97'F in the shade here.

You should get boards and parts that are appropriate for the kind of projects you’re doing.

If you have no need for more pins or features, stick with '328p based parts (Uno / Pro Mini / Nano). Pro mini clones with FTDI adapters for USB<->serial are my go-to for projects, at least once I’ve got the basics working. They’re insanely cheap, so you can leave them in projects without hesitation.

Micro/Leo if you need onboard USB

Mega if you’re doing a 5v project that needs craploads of pins.

There are a few sources for Atmega1284p based boards - these are a nice medium between the mega and 328.

Due if you need lots of software capability, and don’t care that you’ll need a level shifter to interface with 5v hardware (most stuff that works with normal Arduinos).

There are some boards with integrated network connectivity, as well (and also tons of different ways to add connectivity to an Arduino board)