Another SYWT, today it’s time for some Forestry!
Since the removal of the Forestry Mod from Tekkit version 3.0.3 a lot of people have been looking for a way to reinclude the mod into Tekkit. Here is how to add Forestry version 1.4.8.6 to Tekkit version 3.1.1:
- Download the Bukkit server mod here: https://d186ocprvpb7jc.cloudfront.net/mods/forestry-1.4.8.6-mcpc1.2.5.zip and the client mod here: http://bit.ly/Q9Hz9V
- Add a zzz_ to the name of both files so they look like zzz_forestry-1.4.8.6-mcpc1.2.5.zip
- Copy the server archive to your servers \mods\ folder and the client to your games \tekkit\mods\ folder.
- Remove the Forestry stub files from Equivalent Exchange: Open the EE2ClientV1.4.6.5.jar using 7-Zip or a similar archiver thats able to manipulate .jar files and delete the forestry folder in that .jar archive. On the server the forestry folder needs to be removed from EE2ServerV1.4.6.5-bukkit-mcpc-1.2.5-r5.zip too !
- Edit the line mill=4095 in \tekkit\config\forestry\base.conf to mill=4094 to resolve a block-id conflict with the newly added immibis chunkloader block. Make sure You also edit Your servers \config\forestry\base.conf file with the above change !
- Optional: If You dont like to have the twice-than-usual amount of copper-ore and tin-ore generated in Your world You can disable Forestry’s tin/copper generation by editing the line world.generate.copper=true and world.generate.tin=true in Your Forestry base.conf files (client AND server) to both say false.
- Optional: If You’d like to see the Forestry item and block recipes in NotEnoughItems download the NEI plugin here: https://dl.dropbox.com/u/53845448/NEI_ForestryPlugin%201.0.5.17.zip and copy it to Your \tekkit\mods\ folder. This needs to be done on the client only.
DONE 
Now go and have fun in Tekkit + Forestry and read up on all the things the mod has to offer on the official Forestry Wiki !
I hope this SYWT was easy to follow and everything worked out smoothly for You. For reference, most of the information in here was gathered from a thread in the Tekkit forums and through my own experimentation. Feel free to comment if You want to add anything useful to this SYWT !