For me, these are some of the most essential plugins that I use every day. Some other good ones are tabular, renumber, stripansi, matchit, and surround.
I'm also a fan of Pathogen (and tpope's stuff in general), but now I would recommend Vundle. It's like Ruby's Bundler for Vim. The difference is that you define the bundles (plugins) you want to use right in your .vimrc. With :BundleInstall/:BundleUpdate clones/updates these plugins.
I'm not really sold on vundle (or other plugins like it). I don't really like the automation it provides. I'd much rather just install stuff by hand in to ~/.vim/bundle and do my own updates. That way I have maximum control and full knowledge of what's going on in the install process.
Check out PreciseJump and EasyMotion:
http://www.vim.org/scripts/script.php?script_id=3437
http://www.vim.org/scripts/script.php?script_id=3526
(watch the animated gif demos on those pages and be amazed!)
MRU is really useful for navigating the most recently opened files:
http://www.vim.org/scripts/script.php?script_id=521
xptemplate is an awesome, very advanced snippet plugin:
http://www.vim.org/scripts/script.php?script_id=2611
NerdCommenter, for easy commenting/uncommenting blocks of code:
http://www.vim.org/scripts/script.php?script_id=1218
And, of course, before you install any plugin, you should do yourself a favor and install and use Pathogen, or something like it:
http://www.vim.org/scripts/script.php?script_id=2332
For me, these are some of the most essential plugins that I use every day. Some other good ones are tabular, renumber, stripansi, matchit, and surround.