Be sure to choose MLA (Modern Language Assoc.) as "Style Type" unless your teacher has specified otherwise.
If the citation service doesn't have a "Database" category choose "Journal Article" as type of source in most instances.
Cite This For Me: The Harvard Referencing Generator Great new tool. Easy to use interface looks similar to a Microsoft Word doc. No login needed to use unless you want to save your work to finish later. Create a free login to record sources as you go.
EasyBib Bibliography/Works Cited page-maker. Works with 59 types of sources including databases. If you create a free login you can save your works cited/bibliography as you work and export it at the end of your project.
Son of Citation Machine Works Cited & Bibliography Entries Created for you in MLA, APA, Chicago or Turabian Styles. Make sure you select the appropriate type of source (i.e.: book, print article, web article). Also has a Title Page Generator. Make sure you select the correct style!