Need to start some were in modding right? Why not try the Half-Life modding Kit. This Kit is designed to have all the tools you need to start your own Half-Life mod, simple mods can be made or advance ones like Base Defense with this small set of tools. If you want to start modding Half-Life you should try this.
Half-life Modding Kit 2.2 is ready are you? Though it does not look like I have put to much into this update I have, I spent a lot of time looking for the Valve SDKs, and coding and making a few tutorials. Even finding new programs and a compiling tool that is better than Zoner's.