If you need a useful fast lens for a DSLR, why not consider the inexpensive 50 mm 1.8? Canon makes one, Nikon makes one, everyone makes one. They are cheap, they are fast and they are sharp. They are super versatile used as is, and can be excellent for closeups when used with extension tubes (I will cover this in an upcoming post). Normal on full frame and moderate telephoto on an APS-C, they are worth having around.
If you have 100 bucks and no fast prime, go get one (you too, Mike!).
See gallery below for some examples of what it can do.