Why is it that only Iron (and it's products, e.g. Steel) is magnetic? Could Titanium (for example) become ionized to the point of being magnetic?  Does this happen in nature, or via man-made methods which I just don't know about?  What are all metals that can become magnets? Why or why not?

Before going into details, there is a theory in chemistry called quantum numbers. This theory explains that the electrons are not at rest, but they are rotating and spinning in their atomic orbitals. This spin causes a magnetic field. This magnetic field is manifested only if the electron is not paired.
(It is well known that the old theory that claimed that the electrons rotate in circular paths is no longer valid. The new theories say that the electrons exist in so called orbitals, which is a space that can contain up to 2 electrons. If one electron exists, the magnetic properties will be manifested.)

Returning back to our questions, the first category is for the elements or compounds that show some magnetic properties under certain conditions. These materials have unbalanced (unpaired) electron(s) in their orbitals. These unpaired electrons spin, and their spinning creates magnetic fields. Each molecule, hence, forms a magnet. Thus if a magnetic field is applied to  these molecular magnets, they will arrange themselves and align to increase this effect. This type of magnetism is far weaker than the one due to Iron and some other compounds.
Experimentally, paramagnetic property was found to directly proportional to the applied magnetic field, and inversely proportional to the temperature (Curie’s law). There is a famous example in nearly all Physics and Chemistry textbooks showing liquid oxygen being poured between magnetic poles; oxygen is seen being attracted to the poles.

The last type is ferromagnetism. Iron, Cobalt, gadolinium, dysprosium, and Nickel show ferromagnetic properties. These are the materials used to fabricate permanent magnets. In addition to the unpaired electrons, these materials have other magnetic properties described by the Domain theory. This theory proposes that these materials contain microscopic regions called domains, within which the magnetic fields due to atoms are aligned. Their volumes is about 10E-12 to 10E-8 cubic meters. Under normal conditions, domains are randomly oriented, and they have no magnetic effect. However, when they are put in a magnetic field, they tend to perfectly arrange themselves. So maximum magnetic property is achieved. In order to magnetize one of these elements, we use a magnet and we move it on the ferromagnetic metal in one direction; so that domains can be arranged. Or this is done using the magnetic field created from a solenoid, and using it to arrange the domains in one direction.

Returning back to your questions.
Why is it that only Iron (and it's products, e.g. Steel) is magnetic? Could Titanium (for example) become ionized to the point of being magnetic?  Does this happen in nature, or via man-made methods which I just don't know about?  What are all metals that can become magnets? Why or why not?
I guess you can now attribute the answer of every question to a part in my discussion. However, I would like to point out that the magnetic property is because of the electrons and their pairing, because, as I said, oxygen for example may show magnetic properties. So, if  you want to know the magnetism of an element or a compound, look at its electron configuration and you will know how to categorize it.

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Blume, Martin. Magnetism. Encyclopaedia Encarta 1997. Microsoft Corporation.

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Serway, Raymond. Physics for Scientists and Engineers. Saunders Collage publishing, USA. Third updated edition 1990.