My lab contracts with a waste disposal company to discard of organic and inorganic extraction waste and used HPLC mobile phase. If you're in the US, they can probably help you out. I'm sure there are other companies out there, this is just the one we use. Also, there are the obvious state and local (U.S.) waste disposal regulations that need to be considered when disposing of any waste. Their website is copied below.
http://www.cleanharbors.com/
In terms of recycling, I don't have any experience there. I assume it would depend on what type of work you're doing and whether it's practical (in terms of time and money) to try to recycle your used mobile phase or just dispose of it.
