Yep. Dirt. Lots of people are familiar with using herbs, spices, oils, gems, and so on in their rituals - but what about dirt? Mentioned briefly in my post about budget witchcraft/paganism, dirt has a place in ritual and spellwork.
The idea behind using dirt for a working is fairly simple - dirt from a particular location gathers and carries the particular energies of a place. For example, libraries and schools are usually thought of as places of learning, so you might gather dirt from such a location for use in a working involving learning, intelligence, knowledge, and so on.
To give a few more examples, dirt from around a bank may be used for prosperity. Dirt from a garden or farm for fertility or growth. Dirt from around a courthouse for workings dealing with justice or legal issues. Dirt from a mountain for grounding and stability. Dirt from a sea shore (or sand) for purification, dirt from the bank of a swift river for messages. Dirt from a road for travel. Dirt from around a casino or racetrack for luck or gambling. Dirt from the soles of shoes for a working involving that person. Like many aspects of spell work, such things can be open to interpretation, so give some thought to your goal, and the energy you wish to bring to it.
Two types of dirt are often given more attention than others - graveyard dirt, and crossroads dirt. Graveyard dirt in particular has many different rituals and ideas attached to it. Usually dirt is not just taken from any part of the graveyard, but a bit of dirt from a particular grave. This might be someone who has traits specific to your working - such as a doctor for a healing. This might also simply be someone who you were related to, or were close to, while they were alive (particularly for protection). As such, it is important to work to know the spirit you will be working with. Take time to tend to the grave, to leave offerings, to ask for permission to take the dirt, to ask for their aid in your working, to listen to for a response before proceeding.
Again, that is just one view on the use of graveyard dirt. There are tons of different views on the collection and use of such dirt.
Dirt from a crossroads also has multiple associations and rituals attached to it, much as the crossroads themselves. For example, some say you must go during the middle of the night, leave an offering, take some dirt, and leave the area without ever looking back. Other collection rituals might be much less specific. This dirt is often used to add extra potency to any working, but again can carry a variety of meanings.
Now, when it comes to actually using the dirt in a spell or ritual, it's fairly simple. It can be stuffed into a bundle, sachet, or dolly much like herbs can. It can be sprinkled in a ring around a candle (or even added to wax in small amounts when making a candle). It might be sprinkled around an area, such as around the outside of a home in a protective working. Symbols can be drawn onto a paper, the dirt sprinkled on that, and folded into a charm. There are many ways to utilize dirt for all sorts of workings - get creative with it.