if you are in zululand / kwazulu natal- you have to go to ndumu and/or mkuzi- probably best birding in south africa for a small place. If you are around Pretoria in the Gauteng area, there are several excellent day trips- Rust dewinter Dam is very good (once saw 108 birds in a day) as well as Nylsvlei if there is water- these are both big dams with water and bush birds. Around Johannesburg, Marievale is good for waterbirds- again if there is water. at durban you should check out Durban Bay head for waders (need info)There is some great coastal and montane forrest in natal- look into some places there. The Kruger Park is good, but i guess you are not going in- if you do- thge area around shingwedsi is awesome, and the far north -Punda maria/pafuri is where the specials live (pels fishing owl, gorgeous bush shrke etc.) If you are around Lower Sabie check out the sabie dam- it is true that there are not many animals up north- lots of elephants but no lion, cheetah, rhino, leopard or wild dog to speak of
As for Zimbabwe- Vic falls is good- Zambesi national park is good- we got taita's at the falls- you might want to ask a local or two. In Zim, there is really good birding in the eastern highlands- Vumba and Chimanimani- i dont know how accessible or safe they are now but if you have the time (they are far from Vic falls)- check them out- so beautiful and loads of specials like swynnertons robin and augur buzzard.
Field guides- sasol is good. Newmans is old school but i love it. Roberts has got the best descriptions
Anywhere you drive in South africa there are birds on the road- there are some books that tell you where to go like (where to go birding in Gauteng etc.)
Check out fatbirder.com too
I am jealous- last time i was in SA we did the kruger and got about 180 birds in 5 days in the winter and during the biggest cold front storm of the decade during the last 3 days!
good luck
exley