Learning anything about Chibchan languages and related topics is uphill work. There is only occasional agreement on which languages belong in the family, a problem compounded by the fragmentary documentation of many South and Central American languages. There are living Chibchan languages with thousands of speakers that remain barely documented. Much of what work has been done is, of course, in Spanish, and even much of the Spanish-language work is extremely difficult to access -- in unpublished theses, articles in journals that are hard-to-find even by normal academic standards, academic books published in small numbers by Latin American academic presses, or century-old tomes now confined to a few university libraries or the very pricey sections of rare book shops. Hopefully, in future, more material related to Chibchan studies will be published or republished in easily accessible electronic formats.

In English, the best starting points for the modern researcher are probably:

• Adolfo Constenla Umaña, Comparative Chibchan Phonology, (PhD dissertation, 1981). This is technically unpublished but available for purchase in scanned PDF format. The author compares a number of Costa Rican Chibchan (Votic and Isthmic) languages and Muisca (Magdalenic) in order to reconstruct their relationships, including a phonology of Proto-Chibchan and list of reconstructed Proto-Chibchan vocabulary. This is a fairly fundamental work, and pretty much required reading no matter what your own native language is. Constenla Umaña is a giant in modern Chibchan linguistics (his main interest is the Costa Rican languages) and has published numerous other -- alas, much harder to find -- materials.
• "The Chibcha Sphere" chapter (pp. 46-164) in Willem F. H. Adelaar and Pieter C. Muysken, The Languages of the Andes, Cambridge Language Surveys (Cambridge: Cambridge University Press, 2004), which among other things provides a a good overview of Muisca and a reasonable sketch of the Arhuácic languages. Unfortunately, this book is fairly expensive, but as a general reference work on Andean languages it is likely to be found in many university libraries or perhaps even the better sort of public libraries in the English-speaking world.

Beyond these relatively accessible introductory materials, the search seems to become much more difficult.

Second-hand copies of publications like facsimile editions of Fray Bernardo de Lugo's Gramática en la lengua general del Nuevo Reyno, llamado mosca of 1619 and María Stella González de Pérez's Diccionario y Gramática Chibcha: MS anónimo de la Biblioteca Nacional de Colombia can sometimes be found through sites like Abebooks.com without utterly breaking the bank. The latter was published by the Instituto Caro y Cuervo in Bogotá, Colombia, which seems to be something of a center of Muisca studies (though their web page is not terribly forthcoming about this work). There is also Angel Lopez-Garcia's 1995 Gramática muisca, Lincom studies in Native American linguistics (Munich & Newcastle: Lincom Europa, 1995), but reviews of it suggest that it is somewhat problematic. Lincom Europa has also published María Trillos Amaya's 1999 Damana (concerning the Arhuácic language of the Wiwa people in the Sierra Nevada de Santa Marta), and if you can navigate their web shop you should be order a copy (I haven't found this publication offered by any other online booksellers, new or used).

Nicholas Ostler (perhaps best known as author of Empires of the Word, 2005) has written (and co-written) a number of journal articles on Colombian Chibchan (primarily Muisca); his analysis of Muisca sonnets in Fray Bernardo de Lugo's grammar is online in (somewhat oddly formatted) PDF and HTML formats, and an article with Hope Henderson, "Muisca settlement organization and chiefly authority at Suta, Valle de Leyva, Colombia: A critical appraisal of native concepts of house for studies of complex societies" (more archaeological/anthropological than linguistic, but we'll take what we can get!) are his only publications freely available online, as far as I know.

One major clearing-house for Chibchan linguistics (publishing articles from Constenla, Ostler, and most other leading lights of modern Chibchan linguistics) has been the journal Estudios de lingüística Chibcha (from the Department of Liguistics in the University of Costa Rica, where Adolfo Constenla Umaña is based). There is an online list of articles from the journal's inception in 1982 up to about 1996, but no articles themselves, and little information about how one might subscribe to the journal (assuming it's still alive) if your local university isn't a subscriber. A number of articles from the Boletín del Museo del Oro (in Colombia) are online in HTML format, albeit with somewhat mangled formatting and occasional broken links or missing pieces in the older online articles (as far as I can tell). Still, some of the most interesting and valuable pieces in terms of Chibchan linguistics are Adolfo Constenla Umaña's "Sobre el estudio diacrónico de las lenguas chibchenses y su contribución al conocimiento del pasado de sus hablantes" and Robert T. Jackson's "Fonología comparativa de los idiomas chibchas de la Sierra Nevada de Santa Marta".

The Departamento de Antropología at the Universidad de los Andes in Bogotá, Colombia has a wide range of publications, not surprisingly some of which deal directly with Chibchan topics (for example, Lenguas chibchas de la Sierra Nevada de Santa Marta: una perspectiva histórico-comparativa, ed. by María Trillos Amaya, and Lengua de los wiwa y lengua kogui, Gerardo Reichel-Dolmtoff et al.). Unforunately, though their catalog of publications gives prices, it doesn't seem possible to order anything online, and I know of no way to actually get these publications other than by trekking off to the Librería de la Universidad de los Andes (that is, the university bookstore) and hoping they have a copy in stock! In future, perhaps, we can hope they will consider simply distributing PDFs (as presumably much of what one pays for the physical book is intended to cover the cost of producing a physical book, and the cost of producing a PDF would be close to nothing).

Some additional overview information can be found in chapters of Gold and Power in Ancient Costa Rica, Panama, and Colombia, ed. by Jeffrey Quilter and John W. Hoopes (Washington, DC: Dumbarton Oaks, 2003), in which several chapters particularly discuss issues related to past (and present) Magdalenic Chibchan speech groups:

• "Goldwork and Chibchan Identity: Endogenous Change and Diffuse Unity in the Isthmo-Colombian Area", by John W. Hoopes and Oscar M. Fonseca Z.
• "The Political Economy of Pre-Columbian Gold Work: Four Examples from Northern South America", by Carl Henrik Langebaek
• "Gold, Stone, and Ideology: Symbols of Power in the Tairona Tradition of Northern Colombia", by Warwick Bray
• "The Seed of Life: The Symbolic Power of Gold-Copper Alloys and Metallurgical Transformations ", by Ana María Falchetti.
• "Let It Snow: Considerations of the Words for 'Snow' and 'Ice' in the Arhuacan (Chibchan) Languages of the Sierra Nevada de Santa Marta (Colombia)", by Carl Edlund Anderson (a working paper of my own).