Can some of you please tell me what larger soft saddlebags work well if I do not have any side racks for my 2008 GS500F?  I hope to get some saddlebags that are between 25L to 35L per side.  Thank you for your help.  Ride safe.

I'd just like to know where to get side racks. =\

I have a set of Nelson Rigg Spirit 50 saddlebags without side racks. About 23L per side. Weight is the big issue. The plastic fairing is not a load bearing structure, and putting something heavy in a bag causes that side to sag a great deal and the plastic to bend. Light objects are fine, but a gallon of milk or a 6-pack is about the limit. 

Depends on your bags. The ones in my avatar are oxford and have carried both bags weighed down with gear, groceries, etc  they dont sag too much. They have velcro supports that run under the seat, plus pull straps for the top handrail and footpegs and have held up for 5 years of riding. The waterproof covers work pretty well too. If you look around the 35th post on my profile you can see about 3 pics of my bike with bags on.

Use a set of Ventura Manx panniers. About 25litre capacities. They're "OKish", quite strong, but the way in which the waterproofing flaps are arranged makes putting things into them difficult.  Have to organise some protection for the plastics, too.  And Ventura zips generally are in a world of their own - some good, some bad.

Krauser do a rack and side carrier for the gs500
http://www.krauser.de/bike.php?language=2
You have to select gs500 to see the products.

You can attach the these soft sidebags to the side carrier:
http://www.krauser.de/produkte/skyline_bison.php?language=2

H&B also do a complete carrier set. It's like the Krauser one but slightly different (they are made by the same people):
https://www.louis.de/en/artikel/h_b-complete-carrier/10024432?list=14231189 

I talked more about them in this post:
http://gstwins.com/gsboard/index.php?topic=53281.msg818024#msg818024