I just made a doc describing how to setup Texmaker and SumatraPDF with forward and inverse search, but fully portable which is bit tricky. Link to the how-to http://goo.gl/hxDeu (without redirect: http://goo.gl/hxDeu+) or see below:
1. Configuring Texmaker to use SumatraPDF as external PDF viewer with forward search
Open your portable Texmaker and set path to external viewer as follows:
./SumatraPDF/SumatraPDF.exe %.pdf -reuse-instance -forward-search %.tex @
Note that path to SumatraPDF.exe is relative to Texmaker executable and you may need to edit this path to match your folder structure.

2. Configuring inverse search in SumatraPDF
By default SumatraPDF does not allow to configure inverse search via GUI. Run once the following command:
SumatraPDF.exe -inverse-search "texmaker.exe %f -line %l"
You should not change the path to texmaker.exe file, even if you have different folder structure than I had.

3. Create startup batch file
Due to some limitations in SumatraPDF we have to start Texmaker with following batch file everytime we want to use SumatraPDF as external viewer. Place the following commands in texmaker-portable.bat and save this file to the same folder as Texmaker.exe. Also note that you can pass any parameter to texmaker-portable.bat that you could pass to texmaker.exe itself.
@echo off
set PATH=%~dp0;%PATH%
start /D "%~dp0" texmaker.exe %*
4. Run texmaker-portable.bat and test the settings
Troubleshooting
- make sure you are using
-synctex=1
or -synctex=-1
parameter while formatting a tex file
- the tex file should not contain space in its name (Texmaker and SumatraPDF handles spaces just fine, but SyncTeX file may not be created even with
-synctex=1
parameter)
- make sure you started Texmaker with the batch file and SumatraPDF via Texmaker (this chain is mandatory)