If you are a student or Researcher or a scholar then you should use some tools that will help you focus on your Research papers instead of involving yourself in other complexities of formatting,referencing etc.These tools will not only save your time and cost but also will help your papers Academically perfect  to meed the academic standards.

1. For managing papers and references: EndNote, Mendeley, JabRef,
2. For editing LaTeX documents: TeXStudio, Texmaker, LyX (very friendly), etc. ShareLaTeX – online LaTeX editor. Latex installer for windows and latex installer for MAC here.
3. For drawing vectorized figures: Inkscape, Microsoft Visio (both work well with LaTeX). You can also directly use LaTeX to make figures (advanced level)
4. For making graphs from data/results: gnuplot, matplot (I usually use with Python), Excel, MATLAB, etc.
5. For taking notes: Evernote, Microsoft OneNote (both have app on mobile phone)
6. For searching literature: Google Scholar, IEEE Xplore (for engineering students), or just Google. Scientific Journal Finder (SJFinder)  Another search engine you can use is microsoft for academic literature.For academic research on biological topics you can use PubMed Central which is free and contain millions of papers for your topic.
7. For downloading papers: (not recommended though): SciHub, Libgen, etc.
8. For reading PDFs: Mendeley is my first recommendation, you can use it for multiple purposes: organizing/reading/highlighting… papers. If you just want a fast launching tool, try using SumatraPDF, a very light software. If you want to have more powerful tools such as commenting, adding signature then Foxit Reader is one of the best choices.
9. For merging/spliting PDFs: PDFsam
10. For viewing/editing or even compiling codes: Notepad++, Sublime Text, etc.
11. For collaborative documentation, research papers and source codes in addition to version control: Git and Github. 
12. For Figures and Flow charts: Gliffy – draw flowcharts and class diagrams online. Draw.io – another tool for drawing flowcharts online.
13. For Project Planning: You can use Project Plan 365 as project planning tool to create tasks with time lines and deadlines as a Gant chart.– online project planning tool. You can use Gantter which is free and cloud based planning tool.
14. For Statistical testing & Analysis you can use EZ Statistics is a web service that supports some of the most common statistical tests such as T-tests, ANOVA and Wilcoxon. You can also use SISA which allows you to do statistical analysis directly on your browser without going into much detailed requirements. The best thing is you will find user friendly guides to statistical procedures to see what procedure is appropriate for your problem.
15. Sources for Published Books and Research material for international students. Google Books ,The US Library of Congres , Project Gutenberg and National Library of Australia have searchable access to billions of online academic material.

These above tools are very handy and useful for students and scholars to complete their dissertation and research papers. You can suggest some other tools on below comments box that you think might be useful for the students.