I have a drupal site with more than 100000 nodes and counting.
I want to know, how can I increase the site performance dramatically.
There are certain days when traffic is high and the site becomes really slow.
The site also uses views heavily and the frontpage is panels based.
With the same resources I have now, what can I do to increase the performance.
Have a read of Drupal caching, speed and performance, that should give you an idea of where to start. From the sound of it, caching would be a good idea.