[SalesForce] Batch @future calls

(1) To determine the number of Future calls run in the past 24 hours, you can use this utility method:

public static Integer GetNumFutureCallsInLast24Hours() {
    return [select count() from AsyncApexJob 
            where CreatedDate >= :Datetime.now().addHours(-24) 
            and JobType = 'Future'];

(2) To dynamically run methods in a future context ONLY if you have future calls available, you could leverage a "dispatcher" method framework that would run your code in a future context only if you have not surpassed the 24-hour-calls Limit and Call Stack Limit yet:

// Can we run future calls right now?
public static boolean CanUseFutureContext() {
    boolean callStackLimitExceeded = Limits.getFutureCalls() >= Limits.getLimitFutureCalls());

    if (!callStackLimitExceeded) {
        // Check 24-hour rolling window limit
        // of 200 * # of Salesforce, Salesforce Platform, or Force.com One App Licenses
        // *NOTE 1*: These queries may be cacheable depending on your situation
        // *NOTE 2*: If you have not used up all of your allocated licenses,
        // you will have more available licenses than this, so you may need to adjust.
        // However, you can't use SOQL to determine 
        //how many AVAILABLE licenses you have, 
        // only how many have actually been assigned to users
        return GetNumFutureCallsInLast24Hours() < getMaxFutureCallsAllowed();
    } else return false;
}

public static Integer getMaxFutureCallsAllowed() {
    Integer usersCount = [
        SELECT
            COUNT()
        FROM
            User 
        WHERE
            Profile.UserLicense.LicenseDefinitionKey IN ('SFDC','AUL','PID_FDC_FREE')];
    return Math.max(250000, usersCount*200);
}

// Main entry point to your method: call this from a trigger, other class, etc.
public static void RunMyLogic(params) {
    if (CanUseFutureContext()) futureRunMyLogic(params);
    else RunMyLogicMain(params);
}

private static void RunMyLogicMain(params) {
   /* Your logic here */
}

@future
private static void futureRunMyLogic(params) {
   RunMyLogicMain(params);
}

The Limit Methods give you the remaining number of future calls

http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_methods_system_limits.htm

Limit.getLimitFutureCalls()

Returns the total number of methods with the future annotation that can be executed (not necessarily )

Since a future method can't invoke another future call, you can't set up a parallel execution context.

What you can do is invoke future methods in batches from the trigger, say passing in batches of 10 ids per future invocation, so that you can benefit from some sort of multiplier effect.

The other alternative will be to write to a staging custom object from the trigger, which is monitored by frequently scheduled apex.