I decide to give a list with a most important wordpress plugins people use.
There are bunch of social networking plugins, which I dont use on this site.
In wordpress database there are different versions of below given plugins. But the main thing is that below given plugins are proven and wouldnot let you down.
So, heres the list.
Protect from SPAM.
The plugin is MUST. Akismet isthe best way in the world to protect your blog from comment and trackback spam. I didnt activate plugin for one day. In that time I receive around 50 spam comments.
SEO plugin.
With this plugin you can configure various SEO setting. Either for Post or Page or the whole blog. You can change the title , the description etc
Its very valuable plugin for people who know How important SEO is. If you want your blog to be more visible. I am using All in One for experimental purposes, to find out how far this will go.

Show it To SEARCH ENGINES.
Generates XML sitemap. This plugin does very similar thing like previous All in One but in different methods. It helps your blog to become ”famous”. Works for different search engines like google, yahoo and others. For me its default plugin.MUST. There is no point to put anything in web if search engines not seeing it . If its secret , write it on the paper.
BUILD LINKS
Plugin provides some SEO benefits for your site in addition to custom keyword lists, nofollow and much more.I guess its usefull to make your site more like a nework , building links between posts. Its hasnt been useful since I activate it , but It will be , because people who recomended it does not talk nonsense.
Its all about SPEED. W3 Total Cache makes your site faster by cashing different elements. We dont have time to spend minute while your website opens, so its very useful.
Dont forget about BACKUP
Instead of going to your Hosting CPanel, you can do backup through this plugin. Backup is one of the most important procedures to make, in case your site crash. There could be situation , when you install wrong plugin, or accidentley delete some file. Keep it SAFE.