Kile might be my favourite LaTeX editor, although it has the downside of depending on about 40% of the KDE desktop. (This isn't really a big deal, but it does integrate better with Kubuntu than with Ubuntu.) Another downside is that you have to install TeXLive separately for some reason. A plus is that Kile integrates with JabRef, which makes BibTex management a snap.
My next choice is TexMaker. One of the nice things about TexMaker is that it has all the main LaTeX components as dependencies, so installing TexMaker also installs everything you're likely to need to compile your documents. (The only thing I've found missing in 3+ years was a font needed to use an Elsevier document class for a manuscript I was submitting - this was in an additional package.) No JabRef integration though.
If you're used to installing LaTeX + WinEdt on Windows (or TeXShop on a Mac) the install with TeXMaker is a pleasant surprise: Search for it in the Software Centre, click install, go grab a coffee, and you'll be ready to go when you get back. (or sudo apt-get install texmaker if you don't mind the command line.)
Both Kile and TexMaker handle larger projects with many input files well; Kile has a nice Quick Build in that it automatically runs (for example) PDFLaTeX + BibTeX + PDFLaTeX (x2) so that all the references are updated.