1) Emergency fund - figure out how big this needs to be and set aside (savings account, CDs or the like, you won't get much interest but the goal here is return OF money, not return ON money).
2) Mortgage - this depends on your rate, if it is low you may decide to not pay down your mortgage early and instead invest elsewhere (see below). If it is high or variable you may want to pay down early. Also determine if you are actually getting any interest deduction (do you do standard deduction or schedule A, and if schedule A how much of your interest is above the standard deduction) when comparing to other options. Finally, for some there is an emotional benefit in no mortgage so consider how you feel about it even if in theory you might get better long term return elsewhere.
3) International Fund (VXUS or equivalent ETF) - Taxable accounts are the best place for your international stock allocation. So in your taxable space get your international (some sort of ex-US fund) and in your 401k and IRA do the rest. Depending on how much you allocate to international you might have it both in your taxable and 401k/IRA, but the idea is fill up taxable with international first as it is the most tax efficient.