This mod allows you to swap the contents of your hotbar. It started off as a code exercise to work on my Scala, but I found it to be neat so I released it.
By holding CTRL and scrolling, you can swap the bars in your inventory, up or down. Just watch the video, it will get you setup.
This mod is client side only, and will work on both single and multiplayer. Be wary of servers with the NoCheat(plus) plugin, it doesn't like players moving things too fast, the same happens with InvTweaks I think.
The download works on any version of 1.5 and 1.6, source code is also available.
there seems to be a problem with this mod when paired with mods like Forestry that adds backpacks. the forestry backpacks seem to mess up the swapping of the hotbars when you've them in your inventory. it also seems to happen with Dartcraft bags. this may be because these bags/backpacks have several kinds of modes you can switch between...
Thank you for this! It saved me a lot of time! For example, using Railcraft mod, I have 6 or 7 different things that I want... And, when not doing rails, I need 6 or 7 different types of blocks... Now the only thing I need to do is to swap one inventory to another and that's it! Rails, building, glasses, it just works! Great work!