I use a modified version of RefBase. It's an online bibliography database that can also store copies of papers. Useful features include:
- Multi-user capabilities
- Import from arXiv by identifier
- Tagging and grouping of articles
- BibTeX and other formats exported
- Links to webpages and so forth
- Import from a BibTeX file (so you can pass it your bibtex file from a paper) with automatic grouping
My modifications include:
- More mathematical fields (the main developers are geologists)
- MathSciNet import by identifier
- It gets the daily arXiv listing and I can choose which articles to add to my collection
My version is available as a BZR repository at http://www.math.ntnu.no/~stacey/code/RefBase
