The present invention generally relates to systems and methods for producing nucleic acids. In some aspects, relatively large quantities of oligonucleotides can be produced, and in some cases, the oligonucleotides may have a variety of different sequences and/or lengths. For instance, a relatively small quantity of oligonucleotides may be amplified to produce a large amount of nucleotides. In one set of embodiments, oligonucleotides may be amplified using PCR, then transcribed to produce RNA. The RNA may then be reverse transcribed to produce DNA, and optionally, the RNA may be selectively degraded or removed, relative to the DNA. In one set of embodiments, the oligonucleotides may be chemically modified. These modifications may include, but are not limited, to the adding of fluorescent dyes or other signaling entities.