TAP Portugal announced on 06th December the launch of six new destinations starting from June and July 2017: Toronto, Hungary, Bucharest, Las Palmas, Alicante and Stuttgart. You can read the complete press release here.
Bucharest route was suspended on March 27 this year, but will get a fresh start next year.
Most Eastern Europe is free on 15th August (Assumption of Mary) so you can add four more days and get a summer vacation on the spectacular Atlantic coast.
Flights between Bucharest and Lisbon (12-21 Aug) start from €115.
For accommodation I recommend you to search on HotelsCombined as it aggregates all booking portals including Booking. You can find hotel reviews on Tripadvisor which is also great for searching best places to visit.
Hostelworld offers perfect budget accommodation for students, backpackers and low cost travelers.
If you want to stay with a local, you should rent a room, apartment or house on Airbnb. When you travel on Airbnb, you will get €18 in travel credit as my referral.
I suggest to rent a car from RentalCars if you want to drive around Lisbon.