Note: Last update to jQuery Spotlight dictionary was done 19th November 2009. I try to update the docs every month.
You can just hit Apple + Space to enter spotlight and search for jQuery function.
Press and hold Apple + Control + D over any function in TextMate (or Safari, iChat, Mail etc.) to get info popup.
Docs are in your harddrive so they are always accessible. Even when you or docs.jquery.com are offline.
It is native, based on OS X dictionary. No need to install AIR or any other applications.
Download jQuery.dictionary.zip file. Unzip it and move to folder ~/Library/Dictionaries or /Library/Dictionaries. Enable it from Dictionary preferences.
Sometimes it takes a while for Spotlight to see new dictionary. You can speed things up by restarting it.
According to Priit you should also drag new dictionary to be first on the list. This was not true in my case. However if you have problems it is worth trying.
If you like to live in bleeding edge install from Git and build your own.
>git clone git://github.com/tuupola/jquery_dictionary.git >cd jquery_dictionary >make >make install
Thanks to Priit Haamer for the original idea. David Serduke for the the Python script used exporting jQuery wiki to XML format. J�rn Zaefferer whose XSLT stylesheets were used as basis for XSLT stylesheet which converts exported jQuery docs to OS X dictionary XML source