There are tools and there are tools. Some tools are for research, some in the field. Here we are going to cover tools for treasure hunting research (maps, notebooks, data organization), not source (ie. books, magazines, newspaper articles)
Field Tools for Treasure Research
Pen and spiral binder –
the most basic tools used by a researcher. Always have them nearby. How to use them is another matter altogether. Generally, I put a single lead at the top of each page. That page is only for notes on that lead. As I record any information on that lead it is dated, ie. 7/23/2010, then the note is added. Using this method, it keeps the leads very clean and easy to review. What you really don’t want to do is have notes on different leads spread throughout the notebook.
When the lead is developed to a point it consumes the page (front and back) it was given, I rip it out of the notebook and put it in it’s own folder. This way, leads that are worthy must earn a folder. Because you will rip out pages from your lead notebook, you mustn’t use the back of the pages for another lead. Obviously, you’ll want to use the right, not the left, page to start each lead on.
For taking your notebook or lead folder in the field, I use a single carry folder holder. It keeps it protected from rain, wind, mud and dust but most importantly, it keeps it together.
Camera, Tripod/Monopod, Measuring Plumb
From experience in oil and gas fieldwork, I applied a nifty solution to my courthouse research method. When pulling up legal documents at the courthouse, if you use a measuring plumb (just a string of xx inches and a weight) and a tripod you can photograph documents just as good as scanning. It is much quicker and cheaper than from a copy machine. You will need to spend a few minutes at home measuring your plumb and confirming images you took are clear and in focus. The tripod makes it all easier, but with practice you will be able to do it without the plumb or tripod. To keep file size down, set your digital camera to black and white.
Smartphone
Fairly obvious, but I’ll list it here. There are times in the field where you’ll need internet to look something up which will guide your field research. Be sure to have it with you and charged up.
Online Tools for Treasure Hunting
Here I want to cover Online Tools that are useful in doing proper treasure hunting research. These are not research tools or sources, but tools that are peripheral and helpful.
Clustering and Interconnectedness Visualization
Yea that is a mouthful. Basically, it helps in see street credibility of a site by visually displaying the top external web links from it. So if a site is very interconnected with another, then it likely is considered very useful and hence implied with credibility.
TouchGraph
My top clustering Tool is TouchGraph. Here you can see in the picture the fascinating interconnections with other sites.
If you were to apply this to topics of interest, you will quickly discover new sites of relevance that you never new existed and Google-searching missed.
Research Notes and Web Bookmarking
Bookmarks are dumb. There is no user data attached to the bookmark. You may not even know why you bookmarked that web page. If you have other notes on the webpage, you aren’t able to attach that info to the bookmarked page. So because of this, we need a intelligent bookmarking tool.
Zotero
Both Zotero and Evernote fit the bill. Both of these allow you to take notes on the webpage, store source information, or any other meta data you want to attached. Evernote even lets you collaborate.
Zotero is a plug in tool that you can add to Firefox or Internet Explorer. It originally was designed as a bookmark tool for academics that captured the url, the author and publisher information off the webpage to make it easy to cite sources. It evolved and got more powerful. It now is stronger than ever, as Zotero is coming out with a stand alone program as well as an app for your Droid or iPhone. 
I have high regard for Zotero, and encourage this to be one of your core tools during research.
Evernote
Evernote.com is a popular note taking plug-in for web browsers. They have expanded it to other services, but I’m just going to tell you about the note taking side. You can surf the web, find an interesting web page and make a copy of it with a note you write to yourself. You also can tag that note with keywords. Once you make a note, it is uploaded into Evernotes cloud servers and synced with all your other computers that have an Evernote plug in. So you laptop, desktop, iPad, etc. all have the same notes in them.
For example, you surf to a site about green tea, you spot a funky green tea called ‘monkey-on-my-back’ and you make an Evernote to yourself to buy a pound for your uncles birthday. You tag the note as ‘birthday gifts’. Two months later, you remember you found some cool things for gifts, you look into your Evernote account, search for ‘birthday gifts’ and you find half a dozen notes to yourself including the one about this gift idea for your Uncle. 
You can Evernote pictures, web pages, PDFs (and Evernote pro can OCR the contents for you), and just about anything on the web.
Further, if you have a partner, Evernote can be used collaboratively. You just tell it what folders or notes to be shared with your partner. And as long as your partner has Evernote on his computer, he sees the notes you’ve made and shared.
Drawbacks, Evernote only works on Windows and Mac. As a Linux guy, this was a deal breaker.
