The resort 			we stayed                			was really great
The people 			we went             			 were great fun
The tour 			we went         				was quite reasonable
The locals 			we spoke   		 		were very friendly
The man in the market      	I bought this t-shirt   			ripped me off!

which	that	that	whom	
that	which	that	who	
whom	that	whom	from	
to	at	with	on	

The resort 			we stayed                			was really great
The people 			we went             			 were great fun
The tour 			we went         				was quite reasonable
The locals 			we spoke   		 		were very friendly
The man in the market      	I bought this t-shirt   			ripped me off!

which	that	that	whom	
that	which	that	who	
whom	that	whom	from	
to	at	with	on	

Answers	

The resort we stayed at was really great.
(The resort at which we stayed was really great.)

The people we went with were great fun.
(The people with whom we went were great fun.)

The tour we went on was quite reasonable.
(The tour on which we went was quite reasonable.)

The locals we spoke to were very friendly.
(The locals to whom we spoke were very friendly.)

The man in the market I bought this t-shirt from ripped me off!
(The man in the market from whom I bought this t-shirt ripped me off!)

Note:  All of these sentences are about a common everyday topic and are more likely to be spoken or written in an informal style. The second example in each case is possible but would sound far too formal.