Rough Guide to Portugal a good place to start.
Have this and the equivalent LP guide, but we've found that the RG versions have been more use whilst planning the four visits/six weeks we've spent there since 2013.
Plenty of ideas of where to go and what to see or do all over the country. We've done two road trips by public transport to the south of Lisbon in 2013 and north of Lisbon in 2015. We've also had a week in Lisbon in July last year and in Tavira on the Algarve in March this year.
Porto good for wine lodges and exploring the Douro Valley.
Quite a few members of the cycling group my GF rides with have been over to do road biking in the last six months down in the Algarve and we've come across mass participation events in both Lisbon and Tavira.
Lisbon, Evora, Porto, Coimbra, Braga, Obidos are all historical and culture centres, as are Tavira, Sagres and Tomar. Good galleries in Lisbon and Belem (short tram ride from Lisbon). We're not foodies, but have eaten well at family owned, family run cafes or small restaurants all over Portugal (with the exception of one small place down a side street off the main square in Evora back in 2013).
Not done home stays in Portugal - we've used hostels in Porto, Aveiro and Lagos, guest houses in Lisbon, Sintra, Coimbra and Vianna do Castello plus hotels in Tavira and Evora. Pushed the boat out in Sagres (2013) and Tavira this year by staying in a Pousada - got good deals though for b&b and just ate out locally.
We've not hired a car in Portugal as public transport is quite good, but others on here have reccomended car hire as a way of seeing more out of the way places. One car company has however come in for a bit of flak on TT though...
https://www.lonelyplanet.com/thorntree/forums/europe-western-europe/topics/goldcar-my-review?page=1
Hope that this helps!