This is a brief summary of some common place organelles:
First, I'll provide some picture references so you can remember which cell (animal/plant) these organelles are most common.
A typical common-place animal cell.
A typical common-place plant cell.
The Nucleus:
The nucleus is the largest organelle, and contains almost all of the genetic data. The data is organised into chromatin, and is used in protein synthesis, cell division and other processes. Chromatin consists of DNA strands and proteins, and contains the `codes` for proteins. During cell division the chromatin condenses into Chromosomes.
The Nucleolus in the centre creates Ribosomes and RNA, used in creating proteins (protein synthesis).
Molecules may pass through the Nuclear Pores.
Endoplasmic Reticulum (ER):
There are two types of ER - Rough ER and Smooth ER. The difference is that the Rough ER has Ribosomes bound to it whereas the Smooth ER doesn't.
Rough ER transports proteins that were attached to Ribosomes. The Smooth ER is involved in making lipids.
The Golgi Apparatus:
The Golgi Apparatus is a pile of membrane coated sacs, flattened together. It receives proteins and modifies them, maybe adding sugar molecules, then packages the proteins in vesicles.
Mitochondria:
The Mitochondria is responsible for producing ATP (Adenosine Triphosphate) - the `universal energy carrier`, during respiration.
Chloroplasts:
Mainly found in plant cells. The membrane surrounding the Grana (plural of Granum) is the Thylakoid Membrane (more specifically, the Thylakoid stack to produce Granum, therefore the Thylakoid Membrane coats the Grana). Chloraphyll is present on the Thylakoid Membrane and in the intergranal membranes. The chloroplast is involved in Photosynthesis.
Ribosomes:
Ribosomes are very small organelles. They float freely in the Cytosol (the Cytosol is the fluid in the cell, the Cytoplasm is the fluid plus the organelles), and are also attached to the Rough ER. They consist of two subunits. Ribosomes are involved in Protein Synthesis.
Centrioles:
Small protein `microtubules` (fibre strands) either side of the nucleus. They're involved in cell division.