Basically you have two options
Sell it for keys or cash.
Keys you usually get a better deal due to the fact you'd have to actually sell them to make real money. Cash you can still get a pretty good deal and most of the money.
Problems with real money, you'll want to use a middle man who you would trade the item to and would hold it until you receive payment, there are many trusted middlemen that can be found on sourceop/dota2traders. The only other issue is they can chargeback using paypal, you want to ask for them to put in the message of the gift payment 'This is the payment for a good that has been collected and no charge back can be requested' or something to that effect, paypal can still chargeback but I've never had a problem with it.
As for stranges they can sell for a key or two as well, go into the trade chat in the client, check out reddit.com/r/dota2trade and dota2traders.com for price guides and if you are looking to sell.
If you don't need the money keep it, it is quite a nice courier and always nice to have unboxed your own.