We have successfully been running our mixed-league, roto-scoring dynasty league through 4 seasons and are looking to expand the number of teams.
We run an auction each spring and players acquired can be assigned a contract length up to 4 years to keep them on your team. Not to worry if you are a new franchise; there is an expansion draft for new teams to acquire players from the existing franchises, and plenty of star players are currently unowned and available for auction including Lincecum, CarGo, Pujols, Hanley, Mauer, etc.
We use 5x5 roto scoring but with a few different categories. We replaced BA with OBP, and HR with Total Bases. On the pitching side we use Quality Starts in place of Wins, and added Holds to the Save category to increase the value of middle relievers and setup men. 25 man active roster, with 15 player reserve roster, which can be comprised of bench players and minor leaguers. We eventually plan to implement a minor league draft.
League is run on CBS Sportsline. $50 league fee goes toward the prize pool (100% payout, number of places determined by number of teams in the league), plus the CBS fee split evenly amongst all teams (approximately $10-15, again depending on the number of teams). Full league constitution available upon request. Any questions please ask.