Most of the world just thinks of Bacteria and Viruses as "germs" and fails to make any real distinction between them. This leads to any numner of problems from a medical standpoint because often patients doctors demanding a treatment for bacteria when they actually have a viral infection. (The reverse is less common) In reality there are signficant differences between the two, and bacteria actually play a lot of usefull rolls in our bodies and environment, so understanding the differences is pretty important.
Size: simple size comparisons are not really useful as there is a wide range of size differences between types of Viruses and types of Bacteria. For instance if you compare one of the smaller bacteria with one of the larger viruses (Say Chlamydia bacterium and Pox Virus) you will find that their sizes are close to comparable, on the other hand a larger bacterium could be infected by thousands of viruses which means that the viruses would have to be thousands of times smaller. Suffice to say that most Viruses are much smaller than most bacteria.
Living vs. Non-living: While it is generally accepted that bacteria are alive, the jury is still out of viruses. The answer will depend on your definition of life. Viruses are made from organic mater and they replicate themselves according to their own genetic code. They adapt and evolve to their surroundings which is why we continually need new flu vaccines and why there was such a scare about the bird flu moving to humans. All this would make them seem to be alive. On the other hand, they do not use their own metabolic processes to do this. They invade host cells and use the metabolism of the cell to do what they need. (Kind of like if you broke into a Ford plant and used their equipment to make a Toyota while no one was paying attention.) This lack of metabolism leads a lot of people to say that they are not alive. The answer probably lies in where you think they evolved from. If you think that they have their roots in rogue parasitic bacteria that have evolved/devolved to the point where they don't need any of their own structures to replicate themselves, you would probably have to say they are alive. If they came from Rogue DNA or RNA that got out of hand and started replicating themselves in the parent cell, then you probably would think that they are not alive. Suffice to say, the jurry is still out on this issue.
Metabolism & energy: Bacteria acquire and use their own energy through a series of metabolic processes. Viruses use the metabolic functions of host cells, therefore they are by definition parasitic. Bacteria my be parasitic, or not.
Disease: Both of these have the potential to cause disease in humans. While the diseases may mimic each other, the treatments cannot. For example, because Anti-biotics typically target the metabolic functions of bacteria, they cannot be used against viruses. (This is why you don't get an antibiotic for a cold). Because viruses are typically found inside the host cell they are harder to target with drugs, so most antiviral treatments are designed to boost the human immune system so that it can fight the viruses more effectively using systems that are already in place.
Genetic material: Bacteria have DNA and RNA that perform various functions in the cell. Viruses have either DNA or RNA that will perform certian functions in a host cell.