We use tantalum capacitors sparingly, usually only when a datasheet specifies. The element tantalum is a conflict mineral, and it’s expensive. For example the PICs on the Logic Sniffer and Bus Pirate have an internal voltage regulator that specifically calls for a tantalum capacitor. 99% of the time you can substitute a electrolytic in a prototype without problems.
Tantalum caps are polarized. There is a +/- side. + is usually marked by a line etched or printed on the package.
Watch out, these are commonly rated for only 6-16volts. We stock a no-name 10uF/10volt 1206-sized (A case/Kemet A) tantalum and use it in every prototype – even if it calls for a drastically different value.
Tantalum caps are smaller than equivalent surface mount electrolytic caps, but they’re generally more expensive. In a previous partlist post commenters linked to 10uF ceramic caps the same size as tantalum caps, but cheaper. We’re switched to those in new designs.