This is just a group of sites referred to mainly in my Peugeot build but very useful for many bike building projects, with maybe a few others included. These I found invaluable when researching for specific solutions to my own problems. Sometimes they gave me the confidence to buy something over the internet (eBay) with almost a guarantee that the item would fit/work with my other bits. On quite a few occasions they stopped me buying something that would not have fitted and in this way prevented many expensive mistakes. There are lots of other sites out there, forums, facebook (FB has many groups dedicated to specific makes of bike, or specific frame material (e.g. Steel), and many in the groups (especially the vintage oriented groups) are bike mechanics (either amateur or professional) and all seem very willing to give opinions on how to solve a problem (from removing a stuck part to sourcing hard to get items) - I only discovered these groups after I'd done most of my own research, but I've learned a lot on how to solve potential future problems. I'd suggest finding a few groups appropriate to any specific restoration project and asking a few questions if necessary.