For temperature only I prefer the 18B20 sensor. They’re very easy to interface with and they can be at the end of very long wires.

Adafruit has a bunch of sensors that work over the i2c bus; they’ve included python code for accessing the data as well, which makes it easy to get started.

There are sensors out there for everything. Absolutely everything.

https://www.adafruit.com/product/1782

You can integrate just about any sensor into a Pi depending on your knowledge. (any sensor you find on sparkfun would work for someone with a little determination)