My Suggestion (as a similarly afflicted hoarder of Bicycle $STUFF) is to sort through it and decide (be harsh) what you:
1) WILL use
2) MIGHT use
3) WON'T use
Anything in category 1 you clean, and then store for when it's needed
Anything in category 2 you put into a pile for later* ...
Anything in category 3 you the search eBay/here/forums and see if it has any value...then:
If it has some value then take pictures, and then spend an evening listing it on forum/eBay, if you're in no hurry to shift it then list at average price, if you want the space back list at 10-20% below average and accept offers. alternatively head to a local Bike Jumble and sell for 30-40% of eBay prices, it'll soon all be gone and you'll have some cash**
If it's worth peanuts but functional, put it all in a box and take it down to your local Bike Recycling project/charity, there will be one nearby as most cities have one as do some larger towns, they will find a use for your stuff and be very grateful
*...So, back to category 2 stuff, depending on how big the pile of ** cash is and how much room you made it's now time to re-evaluate the pile and move it either to category 1 or 3, be ruthless at this point, you either will use it or you won't, if you still think it's a MIGHT use it case then have a look at how much it;s worth and how easy it is to get hold of and make a decision based on whether you want/need the cash, and if you are happy to hunt one down later or use an alternative part, Vs storing it until the next clearout cycle to see if you still think you will use it.
Go through this and you'll likely end up with a fair chunk of reclaimed space, a small pile of cash and/or a warm feeling inside and some points in the Karma bank, the tricky bit is being ruthless enough, I know I'm often not, which is why I still have vast piles of $STUFF :facepalm: