Well, do you mind selecting up to the whitespace on each side of the word block? Or, or do you have a need to select only up to the word separators, such as a periods and commas -- my.word.com?
If it is okay to select something like " my.word.com ", then there is a nice plugin available via package control install. It is also available here:
github.com/bits/ExpandSelection ... ublimeText
Mine is based on word separators, and can be placed in a whd.py file and a installed in any folder inside the packages directory, e.g. /Packages/User. When saving a python script, you want to have the python console panel open so that you can see if there are any error messages -- usually caused by one or more lines needing a smaller or lager indent from the left-hand margin. Then you need a keymap assignment that calls the plugin, or you can compose a macro that calls the plugin. Mine is a newbie plugin that could be refined further by someone more experienced -- however, it does work.