Suggestions to improve the design & loading speed

I have made a new wordpress theme for my website – http://www.androidapplets.com/

Your suggestions are welcome.
It is a minimalistic design. I want to make the site fast loading. I am not using any plugins. I added related posts, thumbnails etc without the help of plugins. I need suggestion to improve loading speed. Let me know if there is any layout problem in different browsers and mobile devices.

The theme displays first image from the post as thumbnail. resizing is done using timthumb. Will the timthumb script affect the loading speed? timthumb is creating lot of junk files in the cache folder.
Is there any way to generate thumbnails of different sizes without any scripts like timthumb?