I use Lightroom for 99% of all my photography post processing. My workflow for sports photography, as well as everything else I do, goes something like this:
1) Import pictures - in the process, handle keywording, filing into date order on my hard drive, and applying metadata (name, copyright etc). This means photos are already keyworded to some extent as soon as they are imported. When shooting pitchside I'll often be tethered to my PC and Lightroom is running on auto-import, so pics appear immediately on my PC for fast tweaking and sending.
2) Filter out the rubbish - very quickly go through images and flag the ones that I dont want to keep using the excellent shift-X to reject or shift-P to pick/select. Use the shift key to automatically move to the next image.
3) Rank the good stuff - filter on the picked images and rank them with stars, using shift-1,2,3,4,5.
4) Do another trawl of everything ranked 1 or 2 and decide if I want to reject them.
5) Final selection - start editing. I'll crop, level, sharpen, add clarity, lighten faces (using adjustment brush etc), white balance etc. I do this in Develop mode. It's really fast and I can also apply the same edit (e.g. white balance) to multiple images at the same time.
6) Further edit with layers - I'll export to Photoshop for this if I ever need complex layering type edits which is fairly rare. The Photoshopped image then comes back into Lightroom alongside the original.
7) Keywording & captioning - back into Library mode - if it's a sports event I'll keyword the players in shot as you really must do this to remain sane when searching for that image of Danny Cipriani 6 months after the event. I can apply the same keyword to many shots very easily. If I'm sending pics I'll caption them as well.
8) Filing into a collection. I leave Lightroom to organise pics into folders by date on my hard disk and dont worry about where they are. I use collections to order pics within the Lightroom catalogue. For example I have a Sports collection, and within that I have Pro Rugby, and within that a collection per match. I'll put the photos into that specific collection. I also have collections for all my photography genres e.g. monochrome, portraits, landscapes etc, and know that I can have one photo in many collections at once.
9) Export to Smugmug/Flickr - I use Jeffrey Friedl's excellent Smugmug and Flickr export plugins to export direct to those sites.
10) Export with watermarks - I use the equally excellent Image Mogrify plugin to watermark my pics as part of the export process.
11) Create a PDF slideshow - if I'm doing an event/party I'll knock up a slideshow of the top 30 pics as a pdf and email it to the customer. Takes 5 mins and they love it.
All in all, Lightroom is superb. It enables me to process a whole set of 500 shots from a rugby match in an hour, and means I can zap pictures to a picture editor in real time from pitchside. It also catlogues everything for me and allows me to edit without wrecking my originals. It means you dont need to care if an image is a RAW or JPEG - just work with it.
Brilliant bit of kit.
Tobers