SoundFonts are a technology developed by E-MU Systems in conjunction with Creative Labs in the early 1990s. It began as version 1.0 and graduated into version 2.4 in 2005 coming out in the Sound Blaster X-Fi sound card. The file extension began as ".SBK" and then changed to ".SF2" after version 2.0. They can be categorized into groupings called SoundFont banks that can have up to 127 instruments and one drum set. Soundblaster series of sound cards are compatible as well as the E-MU APS. VST plugins such as the SFZ+ Professional allow playback of soundfonts on sound cards that don't have SoundFont native support.
Though there is no specific drum set for hip-hop, the one that is indicative of a good hip-hop SoundFont set is bass drums with a lot of low end. These can be found on the classic Roland TR-808 and TR-909 electronic drum machines.
Hip-hop basslines are right up there with the drums as far as importance. Here you can mix and match with sounds from upright basses to electronic bass from a synthesizer like a Korg-ER1 or the E-MU Mo Phatt.
Hip-hop uses an array of synthesizer sounds from organs to electric pianos to guitar riffs. Sampling from a high-end analog modeling synth such as a Korg MicroKorg or a workstation such as the Roland Fantom series will guarantee an array of sounds that will be high quality.
The most common hip-hop effects are turntable scratches. Knowing a good turntablist with a clean set up will render the best sampled scratches. Along with scratching, looped sections from songs or spoken word phrases are another common effect. This is where you need to tread with caution as the length of the sample can take up a lot of space on the sound card. Also, whether or not the source material is copyrighted also becomes an issue. It is illegal to sample and use copyrighted material if that material will be used in receiving some monetary reward. Clear all samples with the original copyright owner beforehand.