Voltage and Current Sensor for Alternating Current
First, are you sure you need to measure voltage? If you have fixed voltage supply then measuring voltage is only necessary if you need high precision data, otherwise you can assume that your supply keeps it constant.

Second, this is AC, so do you know exactly what you want - amplitude? RMS? both?

In any case, take a look at ZMPT101B module, they are all over the web. And here is a good article on using this module with Arduino. It also explains the importance of calibration and good algorithm to obtain RMS value. Fortunately, Arduino libraries for that are also available.

Now, for current I'd suggest using so called "non-invasive current sensor". It is safe to use by clamping it around one of the power wires and then reading 0..1V output with Arduino ADC. There are cheaper solutions (you can check the selection on same Robotshop site) that require soldering and therefore extra safety measures.

I strongly recommend finding good insulated enclosure which you can use to hide both voltage and current sensor and have only low voltage connections for Arduino coming out. The enclosure would have a cord with plug for your power supply and a socket for plugging the device. If you have 3rd (earth ground) wire in your supply make sure it is properly connected to the output socket. Keep good separation between AC and logic wires.

Once again, safety first. Do not plug your sensor module into power source until enclosure is properly closed.

UPDATE:

Just came across this module: PZEM004T. It is all over the web with tons of videos, instuctables and Arduino libraries. It is also often sold with nice plastic enclosure. With a bit of precaution it can be used relatively safely as a good power meter. Some people add wireless modules to it, so that no physical connection between monitoring device and sensor is necessary.