I used AMX mod in CS 1.6 before. I want to know, what are all the mod's available now for free of cost?
Providing their links also appreciated.
I think your best option is AMX Mod X. The developers of AMX Mod (of which you have experience) joined the AMX Mod X project some time ago. There is an almost comprehensive range of free plugins written by the community that add to the core functionality. I've found that their forums are generally helpful if you can't find what you want or need help with configuration.
Some people still use AdminMod, though I think it's fair to say that they belong to a small minority.