I'm following Friel's Training Bible and am at the tail end of a Build II part of my training. What I can't figure out is which day I should be working in the weight training (for strength maintenance only). Monday's set aside for rest, and the remaining six days I'm out on the bike. I have no problem with a "two a day" workout (if it's called for) - but I'm not sure which of the days would be best.
I prefer to do the weight work out on the evening before a recovery ride day. So for example if I do an interval session thursday and recovery ride friday, I'll do weights thursday night.
But it depends on how much muscle soreness you get from weight lifting, and how long it lasts. It's hard to do the higher intensity rides with sore muscles from weight lifting, not so hard to do the medium or lower intensity rides.
When I used to do weight workouts this time of year, I did them after either a Tuesday OLP bike day or a Thursday zone 2 day. Since the bike is the important workout, I did the weights after. I think this also helps with endurance - you know, at what point in the bike race do you sprint? On a brevet, where do they put the hardest hills? That might be different for MTB racers.